NUMERICAL CONTROL SYSTEM AND METHOD

Abstract: Data items corresponding to a configuration of a work­ piece (11), a finally machined workpiece contour (19), and a cutter shape are entered through a data input unit, and the workpiece configuration and the finally machined workpiece contour (19) are displayed on a graphics display unit. A cutter path (20) subjected to cutter edge compensation is computed from the entered data items, and in one embodiment a finishing allowance is erased from the displayed image along the cutter path to thereby display uncut portions (15,16). The uncut portions may also be displayed by finding intersections (A,B) of the finally machined workpiece contour (19) and machined contour (20) and overlapping the intersec­ tions on the finally machined workpiece contour (19).

Description: NUMERICAL CONTROL SYSTEM AND METHOD OF DISPLAYING IMAGES THEREIN The present invention relates to a numerical control system (hereinafter referred to as an "NC" system) and te a method for displaying images relating to the numerical control system. NC systems are employed to numerically control the position of a tool with respect to a workpiece for machining the latter. NC systems are capable of machining objects of complex configurations with a high accuracy and relatively high production rates. Fig. 1 of the accompcnying drawings schematically shows a numerical control machine tool such as a lathe. A cylindrical workpiece -11 has one end clamped -in -position by a chuck 10 rotatable about a Z axis and the other end supported on a tip end 12a of a tail 12. The lathe has a turret 13 to which is fixed a cutter 14 for cutting the workpiece 11. When the workpiece 11 is to be cut, the turret 13 is moved in the direction of the arrow along the Z axis to cause the cutter 14 to cut the workpiece 11. The cutter 14 has a finite limited cutting angle B, and hence, without changing tools, the workpiece 11 cannot be cut by the cutter 14 to a final contour such as that indicated by a double-dot/dash line in Fig. 2 including surfaces normal to the Z axis. Accordingly, the first cutter 14 is normally effective only to cut the workpiece 11 to a main or rough contour as illustrated in Fig. 3, leaving portions 15 and 16, shown hatched, uncut. To then cut the uncut portions 15 and 16, it has been necessary for the operator to manually measure the uncut portions 15 and 16. Such a measurement process, however, is tedious and time consuming. With the foregoing difficulties in view, it is an object of the present invention to provide an NC system in which uncut portions are computed from a finally machined workpiece contour and the shape of a cutter used for cutting the workpiece anc are then displayed on a graphics display unit, so that the uncut -portions can easily be checked and comprehended without executing an actual machining operation, and a cutt-er suitable for achieving the final contour can easily be selected. A numerical control system according to the present invention includes a numerical control unit for controlling a machine tool, a graphics display unit connected to the numerical control unit, input means for entering a finally machined workpiece contour and a cutter shape, and means responsive to input signals from the input means for effecting cutter edge shape compensation and displaying portions uncut due to the cutter shape as a graphic image on the graphics display unit on the basis of a contour subjected to cutter edge shape compensation, and also the finally machine workpiece contour. More specifically, data items indicating a workpiece configuration, a finally machined workpiece contour, and a cutter shape are entered through the input means, and the workpiece configuration and the finally machined workpiece contour are displayed on the graphics display unit. A cutter path subjected to cutter edge compensation is computed from the entered data items, and a finishing al lasance can be erased from the display image along the cutter path to thereby display uncut portions. The uncut portions mEy also be displ2ited.ty determining intersections of the finally machined workpiece contour and machined contour and overlapping the intersections on the finally machined workpiece contour. The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example, and in which Fig. 1 is a schematic side elevational view of a lathe; Fig. 2 is a fragmentary side elevational view showing the configuration of a workpiece to be machined, a final workpiece contour, and a cutter shape; Fig. 3 is a fragmentary side elevational view illustrating uncut portions of the workpiece; Fig. 4 is a fragmentary side elevational view of a workpiece as displayed on a graphics display unit in an NC system of the present invention; Fig. 5 is a fragmentary side elevational view of the workpiece and a final workpiece contour as displayed on the graphics display unit; ; Fig. 6 is a fragmentary side elevational view of the final workpiece contour and uncut portions as displayed on the graphics display unit; Fig. 7 is a flowchart showing successive steps for displaying a workpiece and a cutter in accordance with the invention; and Fig. 8 is a fragmentary side elevational view of the workpiece showing the intersections of the final contour and the machined contour. The present invention will now be described with reference to Figs. 4 through 8. Figs. 4 through 6 show images as displayed on a graphics display unit in an NC system according to the present invention, and Fig. 7 illustrates successive steps of operation of the NC system of the invention. As shown in Fig. 7, a workpiece configuration, a finally machined workpiece contour, and a cutter shape are entered through an input device into the NC system in a step 1, and the configuration of a workpiece 11 is selected out of the entered data items and displayed on the graphics display unit in a step 2. Fig. 4 shows such a displayed workpiece configuration which is indicated in color, for example. Then, the finally machined workpiece contour is displayed on the workpiece configuration in a step 3. Fig. 5 is illustrative of such combined images displayed on the graphics display unit. In Fig. 5, that portion which is enclosed by the workpiece edges and the double-dot/dash line is shown as a blank, with a finishing-allowance 17 indicated by hatching. Thereafter, a cutter path 18, which takes into account cutter edge compensation, is computed in a step 4, and the finishing allowance 17 is erased from the displayed image along the cutter path 18. Fig. 6 illustrates such an erasing process. As a result of the erasing process, uncut portions are displayed as hatched portions 15 and 16. Alternatively, as illustrated in Fig. 8, a finally machined workpiece contour 19, indicated by the doubledot/dash line, and a cutter shape may be employed as shown in Fig. 8 to extract intersections A and B of the finally machined workpiece contour 19 and a machined contour 20, and information on the intersections A and B may be combined with the finally machined workpiece contour 19 to display uncut portions 15 and 16. It is preferable to employ a color display unit for displaying the finally machined workpiece contour 19 and the uncut portions 15 and 16 in different colors for enhanced visual effects. With the arrangement of the present invention, the NC system is composed of input means for entering a finally machined workpiece contour and a cutter shape, and means responsive to input signals from the input means for effecting cutter edge shape compensation and displaying as a graphics image por-tions uncut due to--the cutter shape on the basis of a contour subjected to cutter edge shape compensation and the finally machined workpiece contour. Accordingly, the uncut portions can easily be confirmed without having to execute actual cutting operations, and a reference is given for selecting an optimum cutter for a desired machined contour. Although certain preferred embodiments have been shown and described, it should be understood that many changes and modifications may be made therein without departing from the scope of the invention.

Claims: Claims: 1. A numerical control system characterised by: (a) a numerical control unit for controlling a machine tool; (b) a graphics display unit connected to said numerical control unit; (c) input means for entering a finally machined workpiece contour and a cutter shape (14); and (d) means responsive to input signals from said input means for effecting cutter edge shape compensation and displaying portions (15,16) uncut due to the cutter shape (14) as a graphics image on said graphics display unit on the basis of a contour (20) subjected to cutter edge shape compensation and a finally machined workpiece contour (19). 2. A numerical control system according to claim 1 characterised in that said numerical control unit comprises a data input unit and a central processing unit. 3. A method of displaying uncut portions in a numerical control system including a numerical control unit composed of a data input unit and a central processing unit for issuing commands to machine a workpiece, and a graphics display unit responsive to said commands for displaying a graphics image, said method being characterised by the steps of: (a) entering data representing a finally machined workpiece contour (19) and a cutter shape (14) into said data input unit; (b) computing a cutter path (20) subjected to cutter edge compensation from said data representing said finally machined workpiece contour (19) and cutter shape (14); and (c) displaying portions (15,16) uncut due to the cutter shape (14) as a graphics image on said graphics display unit on the basis of a contour (20) subjected to cutter edge compensation and a finally machined workpiece contour (19). 4. A method according to claim 3, further characterised by the steps of: entering data representing a workpiece (11) configuration, said finally machined workpiece contour (19), and said cutter shape (14) from said data input unit, displaying said finally machined workpiece contour (19) and said workpiece configuration in overlapping relation, computing a cutter path (20) subjected to cutter edge compensation from the entered data, and erasing a finishing allowance (17) along said computed cutter path. 5. A method according to claim 3, further characterised by the steps of: entering data representing said finally machined workpiece (19) contour and said cutter shape (14) from said data input unit, computing and displaying intersections (A,B) of said finally machined workpiece contour (19) and a machined contour (20) based on said finally machined workpiece contour (19) and said cutter shape (14), and displaying said intersections (A,B) and said finally machined workpiece contour (19) in overlapping relation.

Inventors: SEKIKAWA, KATSUHIDE C/O MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1984
Main classification: G05B19
IPC codes: G05B19