NUMERICAL CONTROL SYSTEM

Abstract: In the numerical control system of the present invention, blades (3a), (4a), ... are provided on at least two crossing sides, or preferably on three sides of a quadrilateral, a blade table (2) is provided which is movable in the directions of a plurality of axes such as the X-axis and the Y-axis, means is provided to store the data of positions of tips of blades when the blade table (2) is at a reference point and to store the diameter of the work. When the work (1) is to be machined with a tool that is selected, the data of the tool selected from said memory means and the diameter of the work are called to calculate the distance from the tip of the tool to the outer periphery of the work, and the tips of blades are moved to the outer periphery of the work. This enables the tool being used to be quickly replaced.

Description: The present invention relates to a numerical control system for automatically controlling a lathe based on numerical information. Lathes that are numerically controlled include ordinary lathes and turret lathes. Many such numerically controlled lathes have tool holders for holding cutting tools, the tool holders being disposed in the longitudinal direction of a workpiece, i.e., the Z-axis direction. In those lathes of the type in which the tool holder is rotated for changing cutting tools, the tools are attached to the tool holder such that the tip of each of the tools will be in the same position with respect to the workpiece when the tool holder is rotated for a tool exchange, so that the tools can be changed conveniently. Thus, when the tool used in a preceding process is retracted prior to cutting a workpiece and the tool holder is rotated to use a tool in the next process, the values of the position of the tool tip on the X- and Z-axes can be used in an NC program as value settings in the coordinate system in the next process. In the aforesaid procedure, the tool that has been used to cut the workpiece in the preceding process is retracted for a tool exchange, the tool holder is rotated to select a tool in the following process, and the selected tool is advanced to a position for cutting the workpiece and moved into contact with the workpiece to cut the workpiece in the next process. Therefore, where different processes are involved, the tool holder is retracted, rotated, and then advanced each time tools are changed, during which time no cutting operation is effected, resulting in a disadvantage in that the cutting procedure is time-consuming. Such operation is carried out in a numerical control lathe disclosed in FR-A- 2 492 716. The present invention has been made in an effort to solve the aforesaid conventional drawback. It is an object of the present invention to provide a novel numerical control system and lathe combination for cutting operation, which is capable of rapidly positioning a new tool for a subsequent cutting procedure, without rotating a tool holder when tools are changed. According to the present invention there is provided a numerical control system in combination with a lathe having: a tool holder, to which a plurality of tools are attached, having at least two sides each having a tool attached thereto; means for moving said tool holder in the directions of plural axes; a holder for a workpiece to be machined by the tools attached to said tool holder; memory means for storing positional data on the tips of the respective tools when said tool holder is at reference points; means for selecting a tool to be used; and means for calling the data on a selected tool from said memory means, computing the distance from the tip of the selected tool to the outer periphery of the workpiece, and moving the tip of the tool to the outer periphery of the workpiece when the workpiece is to be machined by the selected tool, characterised in that said at least two sides of the tool holder extend around the workpiece so that the tools thereon can be selected for operation on the workpiece by moving the tool holder in radial directions without rotating it, and the memory means also stores the diameter of the workpiece to be called by the calling means for use in computing the distance from the tip of the selected tool to the outer periphery of the workpiece. Preferably there are a plurality of tools on each of the sides of the tool holder, and the positional data on the tip of each tool may be stored as a geometric offset amount and a wear offset amount. As described above, a workpiece is disposed in the tool holder which surrounds the workpiece, the positions of the tips of the respective tools at reference points are stored, and the stored values and the distance to the outer periphery of the workpiece are computed to move the tools. When changing tools and cutting the workpiece with a different tool, the tool to be used in the next process can be positioned on the workpiece immediately after the tool used in the preceding process has left the workpiece. Therefore, the time required for a tool exchange is reduced, and the efficiency of a cutting operation is improved. Brief Description of the Drawings Fig. 1 is a view explaining an arrangement of a tool holder and tools according to an embodiment of the present invention; Figs. 2(A) through 2(C) are diagrams explanatory of positional relationships between a workpiece and a tool; and Fig. 3 is a front elevational view of a display screen of a numerical control apparatus. An embodiment of the present invention will now be described in specific detail with reference to the drawings. Fig. 1 is a view explaining an arrangement of a tool holder and tools according to an embodiment of the present invention. Designated at 1 is a workpiece to be cut, which is attached to a chuck on a lathe spindle and rotatable with the spindle. It is assumed that the direction of the spindle is taken as a Z-axis, the horizontal direction as an X-axis, and the vertical direction as a Y-axis. A channel-shaped tool holder 2 has three sides surrounding workpiece 1 and is attached to a lathe such that the tool holder opens downwardly. Tools 3a, 3b, 3c; 4a, 4b; 5a, 5b for cutting the workpiece 1 are detachably attached respectively to the three sides of the tool holder 2, the tips of the respective tools being directed toward the center of the workpiece 1. The tools 3a, 3b, 3c that are directed opposite to the arrow of the X-axis of the workpiece 1 are regarded as a group I, the tools 5a, 5b oriented in the same direction as the arrow of the X-axis are regarded as a group III, and the tools 4a, 4b that are directed opposite to the arrow of the Y-axis are regarded as a group II. Therefore, as illustrated in Fig. 2(A), for cutting the workpiece 1, the tool 3a belonging to the group I has its tip moved to the X-axis on which Y = 0, and then moved into contact with the outer periphery of the workpiece 1. The workpiece 1 can be cut by varying the values on the X- and Z-axes to desired values. The tool 5a in the group III is also moved to get its tip in contact with the outer periphery of the workpiece 1 on the X-axis, and the values on the X- and Z-axes are varied to the desired values to cut the workpiece 1, as shown in Fig. 2(C). As shown in Fig. 2(B), the tool 4a in the group II has its tip lowered along the Y-axis where X = 0 into contact with the outer periphery of the workpiece 1, and the workpiece 1 is cut by varying the values on the Y- and Z-axes to desired values. Operation of the present embodiment will be described below. According to the present system, geometric offset amounts are first established. More specifically, distances are established from the center (xo, yo) of the tip position of each tool when the tool holder 2 is positioned at reference points on the respective axes of a lathe. In establishing the geometric offset amounts, the values of X for the groups I and III and the value of Y for the group II are set as positive, and the other values are combined with respective appropriate signs. Then, wear offset amounts are established, i.e., compensations due to wear on the respective tools are established. The compensations are set such that the direction in which the tools are elongated is regarded as positive and the direction in which the tools are shortened is regarded as negative for X in the groups I and III and for Y in the group II, in Fig. 1, and the other compensations are combined with the signs opposite to those for the geometric offset amounts. Thereafter, a workpiece diameter is set. In machining operation on the lathe, the group names to which the respective tools belong, the geometric offset amount and wear offset amount for each tool, and the workpiece diameter are stored in a memory in an NC apparatus. The data stored in the memory can be displayed on a display screen of the NC apparatus, and the numerical values of the stored data can be added, revised, and deleted as desired. Fig. 3 is a front elevational view showing a workpiece diameter (DIAMETER), group numbers (NO), group names (GP) to which the tools belong, and geometric offset amounts for the respective tools (except for the wear offset amounts), as displayed on the display screen of the NC apparatus. For programming a lathe machining procedure, the tool number of a tool to be used is specified using a T code (tool selection). When the workpiece is cut using the machining program, and a required tool is selected and specified with a T code, the CPU in the NC apparatus calls the geometric offset amount for the selected tool, the wear offset amount for the selected tool, the group name to which the selected tool belongs, and the workpiece diameter from the memory. These data items and the distance that the tool tip traverses from the present position to the outer periphery of the workpiece 1 are computed, and the tool holder 2 is moved to bring the tip of the selected tool into contact with the outer periphery of the workpiece for thereby positioning the tool, as shown in Figs. 2(A) through 2(C). When the cutting process using the selected tool is completed and a next tool to be used is specified by a T code, a process similar to the aforesaid process is repeated to move the tip of the selected tool to the outer periphery of the workpiece. While in the above embodiment the tip position data for each tool is represented by a geometric offset amount and a wear offset amount, the coordinate values of the tip of each tool at the time tool holder 2 is at the reference points may be stored, and the distance from the tool tip to the outer periphery of the workpiece may be computed using these coordinate values. Although the tool holder in the above embodiment is of a rectangular shape having three sides, a tool holder of an inverted L shape having two sides may also be employed. A plurality of lathes to which the present invention is applied may be combined with a robot which supplies workpieces and palletizes them, so that workpieces of different kinds can quickly be machined automatically.

Claims: A numerical control system in combination with a lathe having: a tool holder (2), to which a plurality of tools (3a,b,c,4a,b,5a,b) are attached, having at least two sides each having a tool attached thereto; means for moving said tool holder (2) in the directions of plural axes (X,Y,Z); a holder for a workpiece (1) to be machined by the tools attached to said tool holder (2); memory means for storing positional data on the tips of the respective tools when said tool holder (2) is at reference points; means for selecting a tool to be used; and means for calling the data on a selected tool from said memory means, computing the distance from the tip of the selected tool to the outer periphery of the workpiece (1), and moving the tip of the tool to the outer periphery of the workpiece (1) when the workpiece (1) is to be machined by the selected tool, characterised in that said at least two sides of the tool holder (2) extend around the workpiece (1) so that the tools thereon can be selected for operation on the workpiece (1) by moving the tool holder (2) in radial directions without rotating it, and the memory means also stores the diameter of the workpiece (1) to be called by the calling means for use in computing the distance from the tip of the selected tool to the outer periphery of the workpiece (1). A numerical control system according to claim 1, wherein a plurality of tools are attached to each of the sides of said tool holder (2). A numerical control system according to claim 1 or 2, wherein the positional data on the tip of each of the tools is stored and comprises a geometric offset amount and a wear offset amount. A numerical control system according to any preceding claim, wherein the tools are detachable from the tool holder (2). A numerical control system according to any preceding claim, wherein the tool holder (2) is substantially U-shaped in cross-section. A numerical control system according to any of claims 1 to 4, wherein the tool holder (2) is substantially L-shaped in cross-section.

Inventors: KIYA, NOBUYUKI
Applicants: FANUC LTD.
Application year: 1985
Main classification: G05B19
IPC codes: G05B19, B23Q15, B23B21