INTERFACE DEVICE BETWEEN NUMERICALLY CONTROLLED APPARATUS AND ELECTRIC POWER CONTROL CIRCUIT

Abstract: The invention makes it possible to detect the real speed of a numerically controlled apparatus (NC) of an electric power control circuit (PC), and to control the real speed of the numerically controlled apparatus (NC). An interface device between the numerically controlled apparatus (NC) and the electric power control circuit (PC) is equipped with a memory (50) for real speed onto which the real speed data will be written from the numerically controlled apparatus (NC) and which can read the written data from the electric power control circuit (PC), and is further equipped with a memory (51) for corrected speed onto which the data of corrected speed will be written from the electric power control circuit (PC) and which can read the written data from the numerically controlled apparatus (NC). On the side of the electric power control circuit (CP), therefore, the data is read from the memory (50) for real speed to determine the real speed of the numerically controlled apparatus (NC), and is further written onto the memory (51) for corrected speed to control the real speed of the numerically controlled apparatus (NC).

Description: The present invention relates to an interface unit between a numerical controller and an electric power control circuit (ie programmable controller). A numerical controller NC and a machine tool are usually interconnected via an electric power control circuit commonly referred to as a PC or programmable controller. Fig. 1 illustrates the general arrangement of a conventional numerically controlled machine tool. Reference numeral 1 indicates a microcomputer for numerical control, 2 its bus, 3 a tape reader for converting information punched in a command tape 4 into an electric signal, 5 a manual data input device (MDI) provided with numeric keys and character keys, 6 a CRT for displaying the contents of an NC command program or the like, 7 a ROM for storing a system program or the like, 8 a RAM for operations, 9 a nonvolatile memory for storing the NC command program or the like, for instance, a magnetic bubble memory, 10 to 12 X-, Y- and Z-axis control circuits for driving X-, Y- and Z-axis motors 40 to 42 provided in the machine tool, 13 a buffer, 14 a driver and 15 a receiver. They constitute the numerical controller (NC). Reference numeral 20 designates a microcomputer for electric power control, 21 its bus, 22 a ROM for storing a control program or the like, 23 a RAM for operations, 24 a nonvolatile memory, for example, a magnetic bubble memory, 25 a buffer, 26 a receiver, 27 a driver, 28 a buffer, 29 a receiver and 30 a driver. They make up the electric power control circuit or programmable controller (PC). The numerical controller and the electric control circuit are interconnected via the drivers 14 and 27 and the receivers 15 and 26. Data such as a motor start signal, a tool exchange command signal, a tool number and so forth is delivered from the numerical controller to the electric power control circuit via the driver 14 and the receiver 26. The electric power control circuit responds to the input data to execute predetermined sequence control or the like, causing the machine tool TM to perform starting of the motors, a tool exechange or the like via the driver 30. Information such as the end of the tool exchange or the like is provided from the electric power control circuit to the numerical controller via the buffer 25, the driver 27, the receiver 15 and the buffer 13, and after recognizing the information, the numerical controller performs the next process or the like. It is sometimes desired to automatically control the actual speed (the cutter speed) from the side of the machine tool in accordance with, for example, a load on the machine tool during cutting, or the amount of cutting chip, so as to achieve higher precision or the like. With the conventional numerically controlled machine tool, however, the actual speed is determined by a speed command value in the NC command program and the override ratio. For changing the actual speed, there is no method but to modify the speed command in the NC command program or to manually change the override ratio, so that it is difficult to effect the above said control. An object of the present invention is to enable the electric power control circuit or programmable controller to refer to and instruct the actual speed of the numerical controller. According to the present invention there is provided an interface unit between a numerical controller and a programmable controller which together provide a control system for a numerically-controlled machine tool with the programmable controller being for interconnecting the numerical controller and the machine tool, characterized by the provision of: a machine tool actual speed memory into which the numerical controller writes actual speed data for controlling the machine tool, and from which the programmable controller reads out the written actual speed data; and a machine tool corrected speed memory into which the programmable controller writes corrected speed data which is based on the actual speed data previously read by the programmable controller from the actual speed memory and then corrected in dependence upon machining conditions prevailing, the numerical controller being operable to read this corrected actual speed data from the corrected speed memory and then use it for controlling the machine tool. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing the general arrangement of a conventional numerically controlled machine tool; Fig. 2 is a block diagram illustrating the principal part of an example of the hardware arrangement of an embodiment of the present invention; Figs. 3 and 5 are flowcharts showing an example of processing by microcomputer 1 of Fig. 2; and Fig. 4 is a flowchart showing an example of processing by microcomputer 20 of Fig. 2. Fig. 2 illustrates in block form the principal part of an example of the hardware arrangement of an embodiment of the present invention, in which the same reference numerals as those in Fig. 1 indicate the same parts. Reference numeral 50 indicates an actual speed memory, 51 a corrected speed memory, F1 a mode flag and F2 a set flag. The arrangement of the illustrated embodiment differs from the prior art example of Fig. 1 in the provision of an interface unit which is comprised of the actual speed memory 50 in which the numerical controller can write actual speed data and from which the electric power control circuit or programmable controller can read out the written actual speed data, and the corrected speed memory 51 in which the electric power control circuit can write corrected speed data and from which the numerical controller can read out the written corrected speed data. With the provision of such an interface unit, the electric power control circuit can detect the actual speed of the numerical controller by reading out the contents of the actual speed memory 50, making it possible to determine cutting conditions based on the data. Furthermore, since the electric power control circuit is capable of controlling the actual speed of the numerical controller by writing corrected speed data in the memory 51, it is possible to correct the current actual speed of the numerical controller to a suitable value when it is detected, for instance, by reading out the actual speed memory 50, that the actual speed of the numerical controller is not proper. Fig. 3 is a flowchart of an actual speed calculation process which is performed by the microcomputer 1. The microcomputer 1 executes, for each predetermined period, conventional processing including a current actual speed calculation process (S1) and a process for displaying the computed actual speed on the CRT 6 and, in addition, a process (S3) for writing the computed actual speed in the actual speed memory 50. The microcomputer 20 detects the actual speed of the numerical controller by reading out the actual speed memory 50. When the microcomputer 50 corrects the actual speed, it makes the mode flag F1 a "1" (S10) and then writes corrected speed data in the memory 51 (S11), thereafter making the set flag F2 a "1" (S12). The microcomputer 1 executes, for each predetermined period, such processing as depicted in Fig. 5. When the mode flag F1 is a "0", the microcomputer calculates a speed for use in a pulse interpolation from a speed command value (F) and an override ratio in the NC command program (S21), as in the past, and performs a pulse distribution process at that speed (S22). In the case where the mode flag F1 goes to a "1", however, when the set flag F2 goes to a "1" (S23), the microcomputer 1 reads out the contents of the corrected speed memory 51 (S24) and makes the set flag F2 a "0" (S25), thereafter causing the pulse interpolation to take place at the corrected speed (S26). When the mode flag F1 is a "1" and the set flag F2 a "0", the pulse distribution is continued at the previously computed corrected speed (S27). Incidentally, when the microcomputer 20 detects in step S13 that the set flag F2 has gone to a "0", it lights a lamp or the like provided, for example, in the machine, for notifying an operator or the like of the completion of the speed correction process (S14). In the case of returning the actual speed to the original value, the microcomputer 20 makes the mode flag F1 a "0" and then turns OFF the abovesaid lamp. When the mode flag F1 goes to a "0", the microcomputer 1 calculates the speed for use in the interpolation from the speed command value (F) and the override ratio in the NC command program (S21) and executes the pulse distribution process at that speed (S22), as depicted in Fig. 5, thus effecting control at the original speed. As described above, the present invention is provided with an actual speed memory in which the numerical controller can write actual speed data and from which the electric power control circuit or programmable controller can read out the written actual speed data, and a corrected speed memory in which the electric power control circuit can write corrected speed data and from which the numerical controller can read out the written corrected speed data. Therefore, the electric power control circuit is capable of detecting the actual speed of the numerical controller by reading out the contents of the actual speed memory, making it possible to use the data for determining cutting conditions. Furthermore, the electric power control circuit is capable of controlling the actual speed of the numerical controller by writing corrected speed data in the corrected speed memory, so that, for example, when it is detected by reading out the actual speed memory that the current actual speed of the numerical controller is inappropriate, a process for correcting the actual speed to a suitable value by writing the corrected speed data can easily be carried out.

Claims: An interface unit between a numerical controller (NC) and a programmable controller (PC) which together provide a control system for a numerically-controlled machine tool with the programmable controller (PC) being for interconnecting the numerical controller (NC) and the machine tool, characterized by the provision of: a machine tool actual speed memory (50) into which the numerical controller (NC) writes actual speed data for controlling the machine tool, and from which the programmable controller (PC) reads out the written actual speed data; and a machine tool corrected speed memory (51) into which the programmable controller (PC) writes corrected speed data which are based on the actual speed data previously read by the programmable controller from the actual speed memory (50) and then corrected in dependence upon machining conditions prevailing, the numerical controller (NC) being operable to read this corrected actual speed data from the corrected speed memory (51) and then use it for controlling the machine tool.

Inventors: KAWAMURA, HIDEAKI, OTSUKI, TOSHIAKI
Applicants: FANUC LTD.
Application year: 1985
Main classification: G05B19
IPC codes: G05B19