GB2281789A - A device for control of spot-welding operations - Google Patents

Description

2281789 An IMPROVED DEVICE for COMMAND and CONTROL of SPOT-WELDING

OPERATIONS.

Automatic 'spot-welding processes in industrial production lines, for example bodywork lines for automobiles, are carried out by spot-welding machines controlled by command devices having the following functions:

- adjustment of the electric current for welding; - timing of the welding process; - management and timing of the accessory operations (for example, opening and closing of pliers, synchronisation with external devices, command of cooling water and air pressure for pneumatic valve control, etc.); interfacing with the user; interfacing with a network for remote management of a plurality of welding control devices.

Welding command devices presently in use comprise one or two processors which manage the generation of impulses for the spot-welding machine engager, diagnostics, input/output, serial/parallel ports, interface with the management network, and so on.

Secondly, the processor unit calculates the current necessary for each welding cycle, 2 determines the engagement angle for the subsequent cycle and has also the task of piloting the digital-analogic converter for the activating of a proportional solenoid valve. All of these complex functions are at present performed by known welding command devices using internal programs in firmware on EPROM for the internal and cyclical operative functions, and by a user program on RAM for all the functions, parameters and characteristics relating to a particular operative cycle to be performed.

These user programs, variable and diversified according to individual needs and production typologies, are applicable and modifiable by means of removable connection of a small portable terminal, or can be modified through the logic control and management network of several welding command devices. Normally a welding line is never equipped with one only welding machine and a single command device, but several machines and corresponding command devices all performing the same or different welding operations, and all 91 served by a management network piloted by a remote processing unit managing and modifying in realtime one or more user programs, operative cycle timing, 3 continuous diagnostics both of the network and the single command devices, as well as memorizing executed cycle data, susually termed. operative history.

A single known-type command device, if unconnected to a network, is not able to manage a program timing which is different from that of the RAM user program through the small portable terminal; nor can it modify either specific programs if not by specific manual reprogramming, or perform RAM resident programs. Also, it is not able to operate a timing comparison, as it lacks a reference to absolute time which can only be provided by a network.

Further, a single known-type command device can effect an instant diagnosis in the form of an alarm signal, requiring direct subsequent intervention of an operator, but not a cycle diagnosis and still less an operative history with progressive time reference exceeding a single operative cycle (sometimes even at the level of a single performed welding). Known-type command devices, if unconnected to a network, in the event of power cut are unable to hold even the operative status, lacking an emergency power supply: once 4 the supply is reestablished the device must be reset, as must the relative weldingmachine, before a new operating cycle can begin. In such an eventuality, a RAM with autonomous supply is able to conserve the program, but not the data relating to the job under way.

All of these limitations are due to the lack of a single command device, and have been surpassed by management networks, which through a remote processing unit (often even a conventional personal computer) manage the most necessary user programs, seeing to their timing and comparisons with absolute time, diagnosis, history, and so on.

The term "diagnostics" refers to a battery of data collected from each welding operation, which the command device can visualize in an encoded form on a personal computer display, if connected, or can memorize and visualize on the remote processing unit. For example, some diagnostic data are:

- the outcome of a welding operation, positive or negative, with an error code; - the effective current measured by the command cl device; - the duration of the welding; - the name of the user program used, and so on.

By the terms "history", or "alarm history", reference is made to the memorization of a number, say fifty, of alarms recorded, the programs which have generated the alarms and the absolute time in which they happened. The history can also record data emanating from successful operations.

Network systems also contain limitations and drawbacks. An installation along a multi-equipped industrial production line having several welding machine command devices in a network with only one remote processing unit presents obvious technical complexities, not to mention high costs, so that they are inapplicable on smaller-scale lines needing, for example, only two or three welding machines and relative command devices. For small networks with only a few operating units to manage, the cost of the welding command devices alone is about 20-30 per cent of the cost of the relative totally-networked installation.

There are industrial plants in existence where welding machines manageable with the same user programs in a single network are arranged at considerable distances from one another, distances which can reach up to hundreds of metres, and which cannot therefore be served by the same 6 network, or at most can be connected by expensive network repeaters. In these cases, networks have to be dunlicated.

Faults in the remote processing units lead to isolation of the served command devices which, while awaiting reparation, function within the above-described limits and must be only exceptionally reset and reprogrammed singly and manually by the personal computer: they are, however, without diagnostics and operative history as well as without absolute time reference during the period of isolation.

Finally, user programs are not easily and rapidly transferable from network to network, while single programs or modifications on the command device by means of the perssonal computer are absolutely not duplicable and transferable from device to device.

At present it is therefore not possible to use a user database which can be inserted and rapidly 20 modified device by device in the case of differentiation of the operative or production cycles: instead, an expert technician is needed to reprogram the remote processing unit.

Obviously all of the above-described limitations and drawbacks, even if apparently rather 7 specialized in nature, represent enormous problems in industry, with regard to the continuity and functionality of the automatic lines and relative product quality control.

The principal aim of the present invention is therefore to provide an improved welding command device, able to carry out all of the described functions of the known-type network-served devices, but able to be isolated without all of the limitations and drawbacks of the known-type devices.

The aim of the invention is thus to provide a command device with autonomous absolute time recognition and program timing, autonomous and rapidly applicable, modifiable and duplicable user program memorization, diagnostic capacity and operative history as well as conservation of the operative status in cases where the electric supply fails.

These and other aims are achieved by the improved spot-welding command device of the invention, of the type comprising an input unit (INAL) of the analogic data coming from the users served by the command device and from the external environment, a communication unit (IODIG) with means external 8 to the command device, a ROM memory and a RAM memory, all connected by a bus to a central processing unit (CPU) communicating through an interface (IT) with a port for connection with a portable external terminal for manual programming (T) for management of output and input signals for the command and control, through optoisolator circuits (OIS) and interfaces (COND) with a welding machine (MS) and a relative engager (IS), which is characterized in that it comprises a connector means for removable connection of an external memory (ME) with the bus and the central processing unit (CPU), a clock unit (BOR) directly providing the central processing unit (CPU) with absolute time references for timing operative processes, for diagnostics and operative history, a network supply command unit (PF), equipped with supply sensor means to activate a unit power supply (BT) for continuity of supply to the unit (BOR) and the RAM memory, and also to activate the central processing unit (CPU) for conservation of device operative status; the external memory (ME) transferring welding command operative user management programs to the RAM memory, and receiving device diagnostic data and operative 9 history.

The invention will be better described hereinbelow, with the help of the accompanying diagram, schematically illustrating in a single block diagram of the improved command device according to the invention, with reference to a preferred but not exclusive embodiment of the invention, here illustrated purely in the form of a non-limiting example.

The following description does not contain a detailed breakdown of the structure and functions of the known-type command device, as it is truly well known by technicians in the field, but limits itself to identifying, describing and claiming the improvement in the device of the present invention.

With reference to the accompanying figure, a welding command device of known type comprises an analogic data input unit (INAL) of the users served by the external command device 1. The analogic inputs measure the physical dimensions necessary to the command of the welding point, in particular the measurement of the amperometric reading band of the secondary welding current, measurement of the network tension value of the power unit (of the welding machine engager), measurement of the electrode tensionduring welding.

A communication unit (IODIG) dialogs with means external to the command device through eserial and parallel ports directly managed by a CPU. In particular, the IODIG comprises a serial port 2 for connecting the command device to the local welding network 3 through a special optoisolated interface IR, a serial port 4 for connecting the device to various apparatus through its own general purpose interface IS and a parallel port 5 for connecting it through an interface IT with a printer 6.

A ROM memory is provided, for example in the form of two EPROM memories bearing the internal firmware program for internal cyclical and operative functions of the command device. A RAM memory constitutes the work memory and data bank area, for example constituted by two CMOS chips for a total of 256KBytes in 16 bits, and is destined to memorize and make available a user management program of a specific welding cycle which to command device is destined to manage.

The INAL, IODIG, ROM and RAM units are connected 11 by a bus 7 to the CPU, which last can be in the form of one or more microprocessors.

The CPU is in communication through interface IT with a port 8 for connection, when needed, with a portable manual external programming terminal T of known type. Furthermore, the CPU directly manages a display D which (preferably numerically) visualizes the voltage values read during the last welding operation, and alarm codes, if any.

The CPU also manages output signals 9 and input signals 10 for commanding and controlling, through relative optoisolated circuits OIS and interface COND, a welding machine MS and its engager IS, which are schematically represented in block form in the diagram external to the command device. The CPU manages, for example, all of the diagnostics of the command device and the welding machine, alarms and prealarms, data and signal input/output, serial ports, the interface IR of the network 3 and the interface IT of the external unit, which, as explained before, is usually a portable personal computer; it further calculates the welding current or each operative cycle, generates impulses for the engager IS, closes and opens the electrode pliers, controls the state of 12 the electrodes and the flow of cooling water etc., all necessary functions managed by the internal program on EPROM and the user program available on the network 3 or loaded manually in RAM through the external unit T.

Naturally the command device comprises a supply circuit, schematically represented in the figure by block AL, which supplies several supply lines 11 at different tensions for the various units and circuits of the device.

The improved spot-welding command device of the invention further comprises a connector 12 for removable connection of an external memory ME with the bus 7 and the CPU. The external memory ME transfers the operative management user programs to the RAM memory and also receives device diagnostic data and operative history.

Advantageously and preferably, the external memory ME is constituted by a semiconductor-memory cartridge, an independent firmware management program and an autonomous battery supply, commercially known as a memory card. The connector 12 is constituted by a standard 68-pin connector.

For this memory cartridges with a capacity of 4MBytes are used, of which only a small part 13 (about 2KBytes) is engaged by the user program, with the rest available to the CPU for memorization of diagnostic data and operative history. The considerable capacity of the external memory ME permits the memorization of more than one user program, and can thus constitute a small program band or, on the contrary, it can be dedicated to a simple data bank for the diagnostics.

Advantageously, for consequent program adaptations, commercially-available cartridges can be used, all able to perform various functions as they are provided with external connection and dialog means, modems or peripherals, useful, for example, for remote control of the functions carried out by the device.

The improved device further comprises a timer unit BOR directly providing realtime references to the CPU, for timing operative processes, for diagnostics and operative history, realizable through a simple chip, and also comprises a power failure PF command unit, provided with sensors 13, an emergency battery supply BT guaranteeing supply continuity to the BOR unit and the RAM memory, which also acivates the CPU for conservation of 14 the operative status of the device.

According to the invention, the improved command device can operate, if useful or necessary, in isolation from the network 3, as it can supply the user program through a simple and rapid insertion of the external memory ME, which can function, as has been mentioned, as a mass memory for the diagnostics and operative history data, which last can be printed out by the printer 6 or can be kept in the memory bank. The external memory ME can be used, inserted and disinserted, to apply the same program on various isolated welding command devices, and in this way a user program bank for all needs can be constituted, manageable by non specialist staff. The timer block BOR provides the necessary time references to the CPU, which to date have only been provided by remote processors.

Finally the emergency supply battery BT conserves the operative status during power failures, so that not only data but also user programs in the RAM memory are not lost (external memory ME is provided with its own power supply), nor does the program erroneously recommence as soon as the power is restored.

Naturally the invention retains the interface IR and the port 2 so as to enable it to be connected to the network, just as it retains the interface IT and the port 8 for the portable external unit T, always useful for for changes to the program or for local command when there has been an alarm or like event.

Thus with the invention it is possible to attain great versatility, setting up welding lines even with only one or two welding machines and relative command devices which are connectable to the network but operative in stand-alone conditions.

This obviously allows for considerable savings, and helps to avoid structural complexities in the networked systems. Also, rapid substitution of faulty command devices can be made without long manual reprogramming operations necessarily ensuing, while the operative status and the timing in the external memory ME are duplicable and transferable.

The invention is susceptible to numerous modifications and variants, all entering within the sought protection field. Furthermore, all of the details can be substituted by technically equivalent elements. For example, the external memory ME is practically realizable through the 16 use as a connector 12 of conventional drives for diskettes or magnetic tapes or laser disks, recognizable by the CPU as a extension of the RAM memory, but this solution is not advisable due to the complity of the mechanical means necessary and the relative command programs, as well as because of the fact that the strong magnetic fields present in the proximity of the welding machines detract from the reliability of conventional magnetic supports.

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Claims (1)

1. CLAIMS.

   An improved spot-welding command device, of the type comprising an input unit of analogic data coming from users served by the command device and from outside; a communication unit for communicating with devices external to the command device; a ROM memory and a RAM memory, which together with the communication unit are connected by a bus to a central processing unit; a portable external terminal for manual programming, with which said central processing unit communicates through an interface and a port; optoisolator circuits and interfaces, through which said portable external terminal manages output and input signals for command and control of a welding machine and a relative machine engager; a connector for removably connecting an external memory with the bus and the central processing unit; a clock unit directly providing the central processing unit with absolute time references for 18 timing operative processes, for diagnostics and operative history; a network supply command unit, provided with a supply sensor to activate a unit power supply to guarantee continuity of supply to the unit and the RAM memory, and also to activate the central processing unit for conservation of device operative status; wherein the external memory transfers welding command operative user management programs to the RAM memory, and receives device diagnostic data and operative history.

   A device as in claim 1, characterised in that the external memory is constituted by a cartridge having a semiconductor memory, an internal management program and an independent power supply.

   An improved device, as in claim 2, characterised in that the external memory is provided with external means for connection and dialog with remote apparatus.

   An improved device, according to the preceding 19 claims and as in the description and the accompanying figure of the drawing, and for the set aims.

   5. An improved spot-welding command device, substantially as herein described, with reference to the accompanying drawing.