Abstract:
A number of computer-numerical-control (CNC) machine controllers are associated in the same plant or facility or in related facilities. Each CNC machine controller gathers and stores status information related to the state of operations being performed. A remotely located central computer separately addresses each of the controllers to transfer the status information to a central location where the entire plant or facility operation can be evaluated.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is related to numerical control (NC) and more particularly to computer numerical control (CNC). Numerical Control is the generic term applied to the automation of general-purpose machine tools. Such automation is achieved through electronics and, utilizing computers, such automation has become more flexible and efficient. 
     One advantage of numerical control is the ability to accurately position the axes of a machine and control the cutting feeds and speeds for a machining pattern that can be repeated for each workpiece. This positioning and control information (the NC data) makes up an NC program or part program which is created by a tooling engineer (programmer). NC programs are stored in a memory of the CNC control system (hereinafter referred to generally as the controller) after the programs have been loaded into the memory through a punched tape, for example. In more sophisticated controllers, portions of the NC program can be created and loaded directly into the controller memory by “teaching” the machine with a hand held programmer. Once the NC program is written and stored in the controller, manual action is normally limited to setting up the part, starting the CNC controller which executes the program, and carrying out any necessary manual operations such as tool changes. The NC program, when executed by the controller directs the machine through a series of fabrication steps. For example, where the machine includes a cutting tool the cutting tool is directed relative to the workpiece to make a series of cuts (straight line or circular) in accordance with a series of NC program instructions. These instructions direct the tool as to where the workpiece is to be cut and in what order the cuts are to be made. 
     Most NC and CNC systems are programmed according to a standard of the Electronic Industries Association designated as EIA RS 274-D. The part program information is typically downloaded into the controller from a punched tape reader through an Input/Output (I/O) channel of the controller. However, in more sophisticated controllers, a part program file can be transferred into the controller from a remote, off-line computer through a data link (e.g. telephone line and modem), or a wired or wireless local area network (LAN) or wide area network (WAN). Further the part program information can be downloaded from a floppy disk through a drive in the controller. However, in all instances of part program file transfer, the controller must be in a non-execute state and dedicated solely to the task of downloading the file. A great deal of production time is thereby lost during these downloading or uploading procedures. Uploading is the transfer of data from the controller to an external device, e.g. remote computer, tape, floppy disk, etc. 
     This disadvantage may be overcome by utilizing the multitasking capabilities of a commercially available CNC control system. Such system is the 91000 SuperControl, available from Thermwood Corporation, Dale, Ind. The 91000 SuperControl is a 486 based multi-processor system that operates under an OS-2 operating system, with full multi-tasking capability. With such multi-tasking capability, production down time is reduced by downloading part program files into the controller as one independent task while concurrently running a production program on a part or workpiece as a separate independent task. 
     SUMMARY OF THE INVENTION 
     In large operations, a number of CNC machine controllers may be located within a facility or in a number of related facilities. In order to monitor operations for an entire plant or operation, it would be beneficial to have the capability of communicating with each of these controllers to gather and monitor status information at a single, remotely located computer. The present invention takes advantage of the multi-processor, multi-tasking capability of the Thermwood 9100A SuperControl to provide this capability. 
     As each CNC machine controller, with a multi-tasking capability (e.g. Thermwood 91000 SuperControl) is running a production program on a part or workpiece, it gathers and stores status information in a status file. Then, on a periodic basis or whenever a plant manager elects, a central computer requests the contents of the status file from a selected controller. Such status files can then be analyzed, combined, compiled, printed, etc. at the off-line remote computer while the CNC machine controllers continue to run their production programs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a general block diagram of a CNC machine controller for use with the present invention. 
     FIG. 2 is a general program flow diagram of the status file feature of the present invention. 
     FIG. 3 illustrates an example status file structure in a hard disk. 
     FIG. 4 is a general block diagram of a system with a number of CNC machine controllers in communication with a central remote computer. 
     FIG. 5 shows exemplary data structures for file transfers between the CNC machine controllers and the remote computer. 
    
    
     DETAILED DESCRIPTION 
     The present invention can be implemented in a multi-processor controller with a multi-tasking capability. One such commercially available controller is the 91000 SuperControl manufactured and sold by Thermwood Corporation, Dale, Ind. Although a detailed understanding of such a controller is not necessary for the present invention, a general description is helpful. 
     As shown in the FIG. 1, the controller  10  generally includes a computer  12  with a main memory  14 , in which both the operating system program and part programs may be stored. The controller is a multi-processor system that includes control processor  16 , and Input/Output (I/O) processor  18 , and may include at least an x-axis controller  20 , y-axis controller  22  and z-axis controller  24 . The control processor  16  performs the mathematical calculations and executes all control functions necessary to run the operating system software and NC programs. The I/O processor  18  operates to process input and output tasks and to permit communication between external devices and the controller internal data bus  26 . Axis controllers  20 ,  22  and  24  operate each axis of machine tool  28  by receiving axis movement instructions from control processor  16 , processing those instructions and providing control signals for each axis. Axis controllers  20 ,  22  and  24  also control and process compensation data for each axis. 
     In the Thermwood SuperControl, the “front end” of the controller  10  is a 486 based personal computer (PC) with a 486 PC processor  30  and PC Data Bus  32 . The PC processor  30  provides the control and communication functions for the PC compatible peripheral devices such as display  34 , keypad  36  and floppy disk or hard diskette  38 , and communication between the PC bus  32  and controller internal data bus  26 . The Thermwood SuperControl operates under the OS-2 operating system with full multi-tasking capabilities. The OS-2 operating system is widely known and well understood in the art and a detailed discussion is not required for an understanding and appreciation of the present invention. Under the OS-2 multi-tasking operating system, front-end functions can be performed by PC processor  30  independently of and concurrently with production and machinery functions performed under the supervision of control processor  16 . 
     The present invention takes advantage of the multi-tasking capability of the CNC machine controller  10  to download CNC part program files into main memory  14  while control processor  16  is executing another part program on machine tool  28 . Concurrent execution of these two tasks saves production time and enhances the capability of the controller. Under control of the OS-2 operating system the I/O processor  18  provides the data communication functions necessary to download a part program file into the controller from an external source. An example external source is a physically local hard disk drive  40  that communicates data to the internal data bus  26  through parallel I/O port  42 . Another example is a physically remote computer  44  that communicates through a data link  46  (e.g. telephone lines and modem, RF transmitter and receiver, etc.) and serial I/O port  48 . In the present invention, the data transfer and communication processing takes place at the same time as production processing is being performed by the control processor and machine tool. 
     In addition to downloading CNC part program files into main memory  14  from a hard disk drive  40  or remote computer  44 , and uploading CNC part program files to a remote computer  44 , the present invention takes advantage of the multi-tasking capability of CNC machine controller  10  to monitor certain events and to store certain status information in response to such events. This status information is written to a status file in the hard disk  40 , for example. Ideally, a complete history of all CNC machine operations would be stored in a status file. However, since the hard disk  40  has a limited storage capacity, the size of the status file must also be limited. Therefore, a limit must be put on the time span covered by the status file in order to limit its size. In order to guarantee that the status file will include the most recent data covering a predetermined time span, the status file is created and updated as an older file appended to a newer file. After the predetermined time span has expired, the old file is deleted or cleared, and is replaced by the data in the new file, i.e. by writing the new file data into the old file. The new file is then cleared and new status information is written into the new file as selected triggering events are detected by the controller  10 . 
     The triggering events that cause status information to be read into the status file are determined for each unique application in which the present invention is used. Such events may include starting of the machine operation or part program or stopping the machine operation upon completion, stopping the operation or program during performance (e.g. because of an error) and restarting the operation or program, and detection of certain errors or faults. The status information that will be read into the status file will again depend on the particular application. These may include axis status, axis position, gantry skew, spindle rpm, etc. Through the keypad  36 , the operator may enter certain heading information into the status file, such as current date and time, operator name, part name, tool number, etc. Further, the operator can specify the time span or period over which current status information will be retrieved and stored. 
     Programming methods for file access and storage and data access and storage within files are well known in the art, and will depend on the particular application of the present invention. FIG. 2 is a general flow diagram of the status file feature of the present invention. FIG. 3 shows generally the structure of status file  50  stored in hard disk  40  as old status file  52  appended to new status file  54 . The control processor  16  (FIG.  1 ), under direction of system software stored in memory  14  will gather status information and monitor events over bus  26  or via dedicated status lines  56  and/or event lines  58  connected to various parts of CNC machine controller  10  and/or machine tool  28 . The gathered status data is written to the status file  50  in hard disk  40  via bus  26  and parallel port  42 . 
     As shown in the system diagram of FIG. 4, a machine tool plant or facility may employ a number of CNC machine controllers  10 . Each of these controllers  10  is connected to data link  46 , which is in turn connected to remote computer  44 . The remote computer  44  may be, for example, a  486  based personal computer (PC) with a central processing unit (CPU)  60 , memory  62 , data bus  64 , and standard input/output (I/O) devices such as hard disk  66 , keypad  68  and display  70 . In order to gather information from any or all of CNC machine controllers  10  and to evaluate the entire plant operation, remote computer  44  initiates data transfer requests from specified controllers  10 . The data transfer request will include an address that identifies a particular controller. The transfer request will also identify the request as a read request (i.e. to retrieve a file from the controller) or a write request (i.e. to send a file to the controller). Further, the request may include a file identifier. FIG. 5 shows an example format of a data request  70 . Request  70  may include a read/write bit  72 , controller address field  74  and file identifier field  76 . The file requested for transfer may be a part program file that the remote computer is downloading to a controller, for example, or a status file  50  (FIG. 3) that is to be uploaded to the remote computer. 
     As discussed above, remote computer  44  includes a processor  60  that is programmed using conventional techniques to make data transfer requests on a periodic basis, for example, or as initiated by an operator through keypad  68 , for example. The files transferred to/from remote computer  44  may be stored in internal memory  62 , or preferably hard disk  66 . 
     The data transfer requests are transferred to CNC machine controllers  10  through data link  46 , which may be programmed in a conventional manner to route the request to a particular controller  10  as identified by address field  74 . Alternatively, the I/O processor  18  of each controller  10  may be programmed to monitor requests made through data link  46  and respond only to those requests that contain its controller address. Each controller  10  is programmed using conventional methods to monitor data transfer requests and to respond to such requests through its I/O processor  18 , which will access the appropriate file on hard disk  40 , for example. An example format for a controller&#39;s response is shown in FIG.  5 . Such response  78  may include, for example, a request accept/deny bit  80 , a controller address field  82 , a file identifier field  84 , and if the request was a read request for data from the controller, strings of file data  86  that may be status information or a part program, for example. If the data transfer request  70  from the remote computer  44  was a write request to transfer a file to a controller  10 , and the controller response  78  indicates a transfer acceptance, then the remote computer  44  will send a data transfer  88  in a format shown, for example, in FIG.  5 . Such data transfer may include a controller address  90 , file identifier  92 , and strings of file data  94  (e.g. a part program). The specific data transfer protocol and data formats will depend on the particular CNC machine controllers, remote computer and data link utilized. However, programming techniques and methods for implementing data communication between computers are well known in the art. 
     The present invention provides users of computer numerical control (CNC) systems with a unique capability that has been previously unavailable. Building on the advances of a now commercially available CNC machine controller (i.e. the Thermwood 91000 SuperControl), the present invention takes advantage of its multi-processor, multi-tasking abilities to monitor and store status information about each controller in a multi-controller facility or operation and to retrieve such information at a central remote site. Therefore, an entire plant operation can be analyzed for performance, production and optimization.