Apparatus for controlling and programming welding guns

An apparatus for controlling and programming welding guns, constituted by a set of electronic component circuit boards enclosed in a casing provided with a keyboard and a programming and control display unit which are connected electrically together so as to enable various functions to be performed on the static switches of the welding gun to which the apparatus is connected, namely: a first so-called basic function, i.e. without optional circuit boards being inserted, in which the firing angle of the static switches can be varied as a function of the voltage of the welding transformer primary in such a manner as to keep the energy constant, and further functions which can be obtained by using an optional circuit board, including varying the firing angle of the switches as a function of the constancy of the energy dissipated per cycle in the form of heat during welding, with the number of cycles fixed; maintaining the firing angle fixed and varying the number of cycles with automatic stoppage when welding is complete; varying the firing angle to enable the welding current intensity to be kept constant and varying the number of cycles, with automatic stoppage when welding is complete; and varying the firing angle as a function of the constancy of the current delivered per cycle, with the number of cycles fixed.

DESCRIPTION 
This invention relates to an apparatus for controlling and programming 
welding guns. 
SUMMARY OF THE INVENTION 
The apparatus for adaptive welding control according to the invention is a 
programmable device created for all single-phase resistance welding 
applications using one or two guns controlled by a group of static 
switches, generally two SCRs. 
The main characteristic which distinguishes it is its high level of 
modularity both in terms of hardware and in terms of software. This 
characteristic makes it extremely versatile and adaptable to all present 
and future requirements. In this respect, because of its programmability, 
the welding characteristics can be completely changed while always using 
the same device. 
In its basic configuration, i.e. without the insertion of optional circuit 
boards, the proposed apparatus is functionally compatible with the present 
generation of INDIMO welding controls, with respect to which its 
performance is superior because of the utilization of the facilities 
offered by the use of a microcomputer. With this apparatus, the SCR firing 
angle can be varied as a function of the voltage of the welding 
transformer primary, so as to keep the energy constant and ensure "plant" 
reproducibility. 
In this respect, if the power voltage (500 V) decreases, the welding 
control automatically increases the SCR firing angle so as to deliver a 
greater current, obviously all within certain limits. 
In addition to this characteristic, there are many others which make the 
product technically advanced and of which the description is given 
hereinafter. 
As already stated, the apparatus can be supplied in two versions, namely 
the first basic version which can be programmed only in one mode and which 
will be defined hereinafter as "mode 0", and the second version with the 
ALU circuit board which can be also programmed in modes 1, 2, 3 and 4. 
Greater details regarding the various programming modes and the 
corresponding performance are given hereinafter. 
This apparatus can be programmed with 16 different completely independent 
welding programs which are not dependent on the channel (or gun). Such a 
high number of programs is offered to the user in order to give maximum 
versatility in differentiating the welding spots. It is possible for 
example, when controlling the gun of a welding robot, to differentiate the 
spots according to the number of metal plates concerned in the welding, 
the thickness of the plates and the type of plate (treated or untreated), 
and also according to whether the spots are of primary importance (i.e. 
must be absolutely soft) or of secondary importance (i.e. a small 
percentage of not completely correct spots can be accepted). 
If a spot is of primary importance, it is convenient to program it in a 
mode which is different from 0, using narrow welding irregularity 
intervention thresholds. If a spot is ordinary, it will probably be 
programmed in mode 0. Innumerable combinations and intermediate positions 
exist. 
It is thus possible to execute a succession of welding spots programmed 
heterogeneously, using heterogeneous alarm thresholds. A single spot can 
also differ from another simply by one parameter, which also dictates the 
need for a large number of welding programs. It is also apparent that the 
basic version, although possessing the possiblity of 16 welding programs, 
is less versatile as it allows operation only in mode 0. 
Of the 16 welding programs, the last 4 can be programmed for executing 
thermal cycles. It is thus possible to execute the welding cycles with a 
maximum of 6 pulses each of variable form, for operating on special 
materials which require such treatment. 
In this case, each pulse is programmable independently of the others with 
respect to the following parameters: welding cycles (hot time); interval 
cycles (cold time); angle (energy dissipated); rising slope (&lt;, positive) 
and falling slope (&gt;, negative). With positive slopes equal to .0., the 
first cycle is automatically fired at 87.degree..

DETAILED DESCRIPTION 
The apparatus is in the form of a box 10 composed of a single casing, the 
front side of which carries the panel 11 (FIG. 2) for the guided 
conversation with the operator by means of the keyboard and alphanumerical 
display unit. 
The panel of FIG. 2, illustrated by way of example, comprises the following 
components: a set of numerical keys 12, a set of programming keys 13, an 
installation key 14, a set of switches 15, an LED 16 for indicating the 
presence of the interface board in the processor, an LED 17 for indicating 
the presence of the ALU board, an installation LED 18, a programming or 
modification LED 19, a welding exclusion LED 20, and an alarm exclusion 
LED 21. The alphanumerical display 22 can be seen through an aperture in 
the panel 11. The function of each key of the various LEDs will be 
apparent hereinafter with reference to the operation of the apparatus. 
The main connector for connecting to the welding machine is mounted on the 
rear side of the box 10. This connector has been chosen on the basis of 
its robustness, the large number of insertion and withdrawal operations 
which it can be subjected to (more than 10,000), the high capacity of its 
contacts (8A), and its insulation voltage (1500 V), and allows a damaged 
control unit to be rapidly replaced by a spare unit. 
The mechanical box casing 10, which acts as the frame for the entire 
electronic part, is constructed in such a manner as to allow maximum heat 
dissipation in order to optimize electronic reliability and to ensure 
intrinsic strength. 
The electronic part of the basic configuration functioning in mode 0 
consists of six circuit boards, namely a mother board MD 122, into which 
all the other boards are inserted; a CPU (central processor unit) board 23 
on which the microcomputer controlling all the functions is mounted; a PSM 
(program storage module) board 24 on which the non-volatile working CMOS 
RAM memory is mounted; an IOM (input/output module) board 25, on which the 
opto-isolators and circuitry for controlling the inputs and outputs to and 
from the field are mounted; an MCP (main control panel) board (not shown 
in FIG. 1) on which the keyboard and the alphanumerical display board are 
mounted; and an MPS (main power supply) board 26. 
As already stated, the apparatus also allows optional boards to be inserted 
for increasing its performance, so making it more intelligent, and 
allowing an improved reproducibility of the welding as the external 
parameters vary. In particular, the following can be inserted as shown in 
FIG. 3: an ALU (arithmetic logic unit) board 27, which allows operation in 
modes 1, 2, 3 and 4; a CI (computer interface) board 28, which allows 
serial connection to a remote computer, so making the welding control unit 
an intelligent unit which is decentralized relative to a main processor 
center. The interface can also allow connection to a printer for 
documenting the alarms, the programs executed and the programming in 
general. 
The proposed apparatus has the following special characteristics: 
(1) 16 welding programs; (2) facility for executing thermal cycles in 4 
programs; (3) compensation of the firing angle as the welding voltage 
varies; (4) as an alternative to the first welding cycle at 87.degree., 
programmed insertion of the rising slope (&lt;); possibility of programming 
the descending slope (&gt;); (5) intelligent control of the alarms relating 
to the welding unit with recovery from the abnormal situation (where 
possible); (6) detection of plant errors; (7) self-diagnosis; (8) 
memorizing of the alarm, illumination and installation "history" in a 
non-volatile memory area (black box); (9) 10 opto-isolated inputs (1500 V 
insulation) at 24 V direct current with a common wire; (10) 10 outputs at 
voltage-free contacts; (11) guided conversation with the operator by means 
of a keyboard and alphanumerical display unit; (12) predisposition 
(connector) for rapid diagnosis; (13) automatic setting on installation; 
(14) modular hardware-software concept (optional performance obtained by 
optional insertion of boards); (15) predisposition for rapid replacement 
without reprogramming (PSM board easily extractable). 
The principles of operation of the welding control unit will now be 
described, the description commencing with reference to a general block 
diagram of the apparatus illustrated in FIG. 3. 
All the functions executed are controlled by the microprocessor on the 
board CPU 23, which for this purpose utilizes a working memory of 256 
bytes, a CMOS RAM program memory 31 having a capacity of 1K or 2K 
according to whether the scheduled operation is normal (mode 0) or 
multi-mode (mode 0, 1, 2, 3, 4), and the system control software memorized 
on the EPROM 30. 
The microcomputer, consisting essentially of a microprocessor, receives at 
its input the following signals: data originating from the keyboard 11 
during the program writing stage; data originating from the memory RAM 31 
during the program execution stage; signals of external origin by way of 
the input/output IOM board 25; special signals indicating the state of 
operation of the control unit; plus the necessary supply voltages. 
In its turn, the microcomputer feeds the control signals for operating the 
functions performed by the other boards. 
The signals for the interactive conversation between the operator and the 
apparatus are exchanged between the front MCP board 32 and the CPU board 
23. In particular, the data set by the operator reaches the CPU 23 from 
the keyboard panel 11 and the relative coder, and the CPU 23 feeds the 
signals corresponding to the various messages to the alphanumerical 
display unit 22. 
The compiled programs are memorized in the RAM memory 31 on the PSM memory 
board 24, and are then recalled by the CPU 23 during execution. This data, 
suitably processed, is fed to the input/output IOM board 25 for subsequent 
feeding to the field. Likewise, the signals of external origin indicating 
the state of operation of the welding machine reach the CPU by way of the 
same board for suitable processing. 
The optional boards ALU 27 and the processor interface CI 28, if inserted, 
exchange their signals with the input/output IOM board 25. 
Finally, all the boards are connected together by the mother board MB 122 
on which there is also the connector for connecting to the field. 
A description will now be given of each board and its function with 
reference to the drawings illustrating each block diagram thereof. 
The front MCP board 32 has the block diagram of FIG. 4. The keyboard on the 
front board is organized in the form of a matrix consisting of 4 rows and 
8 columns. The row-by-row scanning of each matrix is controlled by the 
decoder 40, which at its input receives the row selection signals from the 
keyboard and display control 41. As soon as it is verified that a key has 
been pressed, 42, in one of the rows, a word of 8 bits corresponding to 
the said key is fed to the control section 41. 
In its turn, the control section 41 receives commands from the CPU 23, and 
feeds the switching request signal to the CPU. 
On receiving the control selection signal or reading signal, the bus 
receiver-transmitting 43 is activated so that it feeds the data from the 
keyboard 42 to the CPU across the connector pins on the mother board MB 
22. 
However, if only the writing signal is present, the data from the CPU 
across the pins is fed for its display to the display board 44 by way of 
the receiver-transmitter 43. 
The cyclic selection of 4 chips of the display board 44 is done by a 
multiplexer decorder 45 which at its input receives the addresses from the 
address bus 50. 
The PROM 46 activates the mutliplexer 45 and the writing of the display 
board 44. 
On the front board of FIG. 4 there is present an integrated circuit 47 with 
8 flip-flops of type D for illuminating the LEDs 48 present on the front 
panel 11. 
The integrated circuit 47 receives the data word at its input, and its 
contents are updated each time a specific writing command for that 
register is emitted. 
The four switches 15 on the front panel 11 feed data relating to their 
state by way of the pins. 
Finally, it should be noted that all signals originating from the CPU or 
fed to it are also present at a special connector 49 mounted on the front 
board. 
This connector, connected either to a specific apparatus (simulator) or 
simply to a logic analyzer, is used for the diagnostic operations which 
allow any fault to be identified. 
The CPU board 23 is shown in FIG. 5. 
This board represents the heart of the entire apparatus, and is formed by a 
microprocessor 53 together with the control circuits for the data bus 52, 
the address bus 50 and the command bus 51, constituted by a data buffer 
54, address buffer 55 and command buffer 56 respectively. 
The software used by the CPU board is memorized on EPROM memories 57 for a 
total of 10K bytes. 
These memories are addressed with bits from A.0. to A11, and their outputs 
are connected to the data bus 52. 
The CPU uses the 256 bytes of the integrated circuit 58 as its working 
memory. 
A counter 59 and a comparator 60 for determining the firing zone are 
connected to this integrated circuit. 
As the mains frequency passes through zero, the counter 59 is zeroed and 
then begins to count with the clock generated by the time base generator 
61. 
When the counter contents equal the data from the integrated circuit 58 
corresponding to the firing angle set by the operator, the comparator 60 
feeds a firing zone recognition bit to the microprocessor 53. 
Simultaneously, a gate of the integrated circuit 58 feeds a bit 
representing the firing activation signal to the circuit which controls 
the pulse transformer 62 of the external firing unit. 
If in addition to the firing zone recognition signal and firing activation 
signal, the signal indicating the presence of voltage at the SCRs of the 
detector circuit 63 is high, the pulse transformer 62 mounted externally 
for firing the SCRs becomes operated. 
The signal of the time base generator 61, which is fed to a hardware 
control section 64, is generated together with other signals, by the 
programmed time base. 
This circuit is formed from two cascade-connected counters, of which the 
clock signal is that fed by the integrated circuit 58. 
The counter outputs represent the address inputs of a PROM 65 programmed so 
as to feed to flip-flops signals corresponding to those of the time base. 
The voltage of the welding transformer primary, which is reduced to low 
voltage by a sensor mounted on the machine, is fed to a circuit 66 which 
transforms it to a digital value and preserves its value in a register 67. 
The output of this register at the data bus is used by the CPU for any 
variation in the firing angle in mode 0. 
The cos .0. signals arrive automatically from the external firing unit for 
identifying the presence of voltage at the SCRs and the presence of power 
voltage at the welding plant respectively, by way of suitable circuits 63 
and 68. 
An alternating voltage of 20 V is fed from the power supply unit 69 for 
generating a square wave form of 50 Hz at 69'. 
The wave form is fed both to the outside for controlling the software, and 
to the inside of the board itself to a circuit which generates a pulse for 
each transit through zero. 
The PSM program memory board 24 is illustrated in FIG. 6. The RAM memory 70 
used for memorizing the programs set by the operator, and as a "black box" 
for memorizing the alarms, consists of two chips of 1K words of 4 bits, 
thus obtaining 1K words of 8 bits. When expanding to the modes 1, 2, 3, 4 
by means of the ALU board, it is necessary to mount a further 1K.times.8 
bits. 
For the electrical supply and control of the operation of the memory, the 
board receives signals which, when suitably correlated as indicated in 
summary form in FIG. 6, are used to provide the activation signals at 71, 
the reading or writing command, and the supply to the memory chips. 
On the memory board 70 there are also three rechargeable batteries having a 
capacity of about 150 mA/h, to act as buffer batteries. They are 
automatically recharged during operation, and when fully charged have a 
life of about 2 months. Their purpose is to keep the memories supplied 
during the period in which the apparatus is switched off, so that the 
memorized data is not lost. It should be noted that if the PSM board is to 
be kept at rest for a long period, it is necessary to disconnect the 
batteries, by operating the appropriate microswitch. 
The IOM board 25 (input/output module) is shown in FIG. 7. 
The basic element of the IOM board is the programmable interface 80 which 
controls all the functions performed by the board. At its input, this 
integrated circuit receives command signals from the CPU, and the signals 
at the output from its gates are fed to the two pilot stages 81 and 82 
which feed them in their turn to the output circuits 83. 
The input signals from the field reach the input circuits 84, and pass from 
these to the interface 80. 
Each output circuit (FIG. 8) is constituted by an LED 85 at digital 
electronic level (+5 V), which is illuminated if the relative signal is 
present, an optical isolator 86, and a relay 87. 
A 3 A fuse is also formed at each output by means of a constriction in the 
printed circuit track (localized rupture). 
If a deformity occurs, this signifies that the relay is not functioning 
correctly, and consequently the circuit breaker cutout signal is emitted. 
All this is necessary to prevent any accidents due to undesirable closure 
of the welding solenoid valves. In this respect, if the signal at the 
welding solenoid valves is not the correct one, the welding operation is 
immediately interrupted. 
Each input circuit (FIG. 9) is constituted basically, in a similar manner 
to the output circuits, by an optical isolator 86 and by the LED 85 
indicating the input presence of the relative signal at digital electronic 
level (+5 V). 
Besides the input and output circuits and their control stages, the board 
also comprises the circuit which checks any malfunctioning of the software 
89 or hardware 90. 
Finally, three further circuits are present on the board for the following 
checks and controls: 
checking whether the mains voltage is outside tolerance, 87; 
checking whether the control or power supply unit is at excessive 
temperature, 88; 
controlling the pulse transformer, 91. 
The MPS board 26 (main power supply) is shown in FIG. 11. 
The mains voltage passes through the mains filter 96 to the two primaries 
97 of the supply transformer 98. The following voltages are available at 
its five secondaries: (1() 9 V-10 A; (2) 20 V-4 A; (3) 17 V-1 A; (4) 17 
V-1 A; (5) 20 V-0.5 A. 
The first four voltages are treated in a similar manner so as to obtain the 
required values as output. More specifically, each voltage is rectified by 
a diode bridge 100, filtered by a group of capacitors 101, regulated by a 
voltage stabilizer circuit 102 except for the 20 V voltage, further 
filtered by a capacitive output filter, and finally fed to the board 
connector. An LED diode 104 is also present at each output to indicate the 
presence or absence of the corresponding voltage. 
In contrast, the 20 V voltage is fed from the fifth secondary to a squaring 
circuit 103 and then to the connector for suitable use by the CPU. 
It should be noted that the parts enclosed by the dashed and dotted lines 
in FIG. 11 are not mounted directly on the power supply board. More 
specifically, the stabilizer circuits are mounted on the heat sink, on 
which the thermistor is present for recognizing excessive temperature. 
The mother board MB 122 forms the core of the apparatus. It is disposed on 
the base of the apparatus, and on it there are mounted the connectors into 
which the other boards are inserted, plus the connector for connection to 
the field. The tracks of its printed circuit form the signal 
interconnections between the various boards. 
The apparatus is arranged to accept both hardware and software on optional 
boards which widen its performance. These boards are two in number, 
namely: 
the adaptive ALU board 27 for operation in modes 1, 2, 3 and 4; 
the computer interface CI board 28 for connection to a remote computer or 
printer. 
The ALU (arithmetic logic unit) board is shown in FIG. 12. 
The ALU board is composed essentially of two analog channels 110 over which 
signals are fed proportional to the welding voltage and current. The 
signals, from which any disturbances which may be present are removed, are 
fed to the automatic self-setting circuit, and converted by suitable 
circuitry 112 into numerical data which can be processed by the integrated 
circuit 113 which operates as a multiplier/accumulator. The three output 
registers can be read by the main microcomputer which controls the 
apparatus. 
The CI (computer interface) board 28 is shown in FIG. 10. 
The CI board is constituted essentially by a programmable communication 
interface 94 which converses with the field by means of current loop 
serial line control devices. 
A programmable particle generator determines the line 
reception-transmission speed. 
The program relative to outside communication is located in the EPROM 95. 
A further characteristic which distinguishes the apparatus according to the 
invention is the facility for compensating the firing angle as the welding 
voltage varies (mode 0). 
The control unit controls the power SCRs at the welding transformer, by 
firing them at a predetermined angle during the cycle (FIG. 13). 
The transformer T.sub.VP across the primary of the welding transformer 
(FIG. 14) takes the voltage present and reduces it to safety levels of 
about 5 V, to then feed it to an analog/digital converter which converts 
it into a number of 8 bits. The half wave is thus divided into 256 voltage 
levels. Likewise, the 180.degree. angle of the half wave is divided into 
256 parts, each equivalent to about 0.703.degree. (FIG. 15). 
The control unit recognizes a minimum voltage change of 1/255, and 
consequently varies the firing angle by a quantity suitably calculated so 
as to maintain the power fed to the welding gun constant. FIG. 16 shows 
the relationship between the welding voltage and current. 
Tables can thus be drawn up showing the relationship between the angle in 
electrical degress and the angle set during programming, and also between 
the measured cos .0. of the phase displacement between i and v, the 
effective cos .0., the electrical degrees and the angles to which certain 
welding power percentages correspond. It should be noted that set angles 
greater than those corresponding to 100% of the welding power do not 
contribute anything further beyond the maximum. 
Alternatively, on commencing welding with a firing angle of 87.degree., it 
is possible to insert a certain number of rising slope cycles. Likewise, 
the falling slopes are programmable, i.e. the control unit initially fires 
the SCRs at a small angle, to then rise to the angle programmed in the set 
number of cycles. If for example the programmed angle is 200 with two 
cycles of rising slope, the connected microcomputer calculates the welding 
power corresponding to the set full working angle (200)', divides the 
calculated value into three parts, and seeks the angle corresponding to 
this power, with which it fires the SCRs in the first slope cycle. For the 
second cycle it seeks the angle corresponding to 2/3 of the total power, 
to finally reach the third cycle, i.e. the full working cycle, at the 
angle corresponding to the total power. 
In this manner, by using the microcomputer the apparatus operates linearly 
on the welding power. 
During welding, a situation in which one SCR does not fire during a half 
wave whereas the second SCR fires normally during the opposite half wave 
must be prevented. If this happens, the transformer becomes saturated with 
the possibility of seriously damaging the static switches. It is therefore 
necessary for the two firing angles in the positive and negative half 
waves to be absolutely identical. If this is not the case, the apparatus 
seeks to make-up the firing operation which did not take place. If for 
example during the first welding cycle there is no firing during one of 
the two half waves, the control unit allows the next half wave to pass and 
then again attempts firing during the half wave corresponding to that in 
which the firing previously failed. 
This entire procedure is repeated for a maximum of five times, after which 
an error warning is given. If the firing fails during the cycle following 
the first, the described procedure is repeated only for a maximum of two 
times, so as not to alter the thermal characteristics of the welding spot. 
The sensors mounted on the welding transformer, namely one in mode 0 and 3 
in modes 1, 2, 3 and 4, make it possible to indicate operational 
irregularities in the system. In the case of three sensors, the diagnosis 
is more accurate. 
The apparatus is able to carry out automatic fault diagnosis, giving a 
relative alarm in the case of malfunction. The more significant checks are 
as follows: 
(1) Hardware blocked: this alarm acts directly on the outside with a 010 
output, to cause cut-out of the circuit breaker which, if connected 
externally, switches off the apparatus; 
(2) Software blocked: if at every 40-50 msec the software does not give an 
indication of correct operation, the effect is similar to that in the case 
of hardware blocked; 
(3) Electrical supply incorrect: this checks whether the apparatus supply 
voltage varies beyond a range of .+-.15% of the rated value. If this 
happens, it continues to execute the set programme but indicates 
malfunction of the system; 
(4) CMOS RAM programme memory soiled or faulty; 
(5) Excessive temperature: the apparatus checks that the temperature does 
not exceed +100.degree. C. in the heat sink on which the stabilized supply 
units are mounted, and +70.degree. C. inside the device. 
A certain number of cells of the non-volatile RAM memory is reserved for 
memorizing the alarms, illuminations and installations which have taken 
place during operation. These operate as a "black box" to give easier 
indentification of the recent control history. 
The apparatus possesses 10 opto-isolated inputs and 10 outputs at 
voltage-free contacts, so enabling loads to be controlled both at +24 
V.d.c. and at 110 V.a.c. 
The alphanumerical display unit of 16 characters and the keyboard on the 
front panel allow conversation between the operator and the apparatus. 
In addition to operating mode 0, the control unit can also operate in modes 
1, 2, 3 and 4, as stated. 
When fitted with the ALU board, the apparatus provides further performance 
beyond the basic configuration, and is able to read the instantaneous 
welding current, voltage and power, and to control a very large number of 
welding parameters. 
The following further performance is possible: Welding in mode 0 with 
monitoring of the cos .0. and welding current bands during the pulse full 
working cycles if the programmed pulse is single, or of the last one if it 
is multiple. 
This is used for recognizing welding errors, such as the type of 
short-circuit welding (absence of plates), secondary circuit damaged or 
interrupted (braiding to be inspected and replaced if necessary etc.), 
ferromagnetic masses close to the welding machine which considerably vary 
the operating conditions, so influencing welding. 
Welding in mode 1 with the firing angle variable as a function of the 
constancy per cycle of the energy dissipated in heat during welding, and 
number of cycles fixed. 
This is used for very accurate welding with high reproducibility for equal 
surrounding conditions, i.e. plates, electrodes etc. In general, the 
welding is 10-20% longer in terms of numbers of cycles than the 
corresponding welding in mode 0 (in order to obtain the same effect). 
Welding in mode 2 with fixed firing angle and variable number of cycles, 
with automatic stoppage when welding is complete. 
In contrast to the welding control units presently available commercially, 
which make a reading on a single spot for each welding cycle (normally 
they read the voltage and current where di/dt=0), the apparatus uses the 
integral both of the current and of the voltage, so minimizing any errors 
due to false readings in positions coinciding with disturbances. 
This welding mode is used where the surrounding conditions (number of 
plates, plate thickness, electrode deterioration, power voltage variations 
etc.) vary. Typically, it is possible by using this welding mode to 
compensate for a variation in the surrounding conditions which are in the 
ratio of 1:2 (.+-.50%). 
As an example, if the correct parameters are set for welding two plates 
having a thickness of 1.6 mm, the automatic control system will operate 
correctly to enable three (1+2) plates of 1.6 mm, or two plates of which 
one is 1.6 mm thick and the other is between 0.8 mm and 2.4 mm thick to be 
welded. This ratio is not the maximum value, but only a typical value, but 
by further varying the ratio the welding becomes carried out less 
correctly in that it would be necessary to change both the size of the 
welding tip and the pressure with which the electrodes act. These 
parameters cannot be controlled by the apparatus. 
Welding in mode 3 with the firing angle variable so as to keep the welding 
current intensity constant (by setting the CURRENT), and with the number 
of cycles variable, with automatic stoppage when welding is complete. 
This is used for welding where maximum adaptability is required. The 
typical adaptability ratio is 1:1.5 (.+-.66%). It operates effectively on 
dirty and/or processed (zincrometal etc.) plates. 
For example, if the parameters are set for correctly welding two plates 
each 1.6 mm thick, mode 3 easily allows welding of two plates both 0.8 mm 
thick, or three plates all 1.5 mm thick, or four plates of 1.5+0.8+0.8+0.8 
mm thickness. It is less effective than mode 2 in terms of compensating 
for electrode wear. 
Welding in mode 4 with the firing angle variable as a function of the 
constancy of the current delivered per cycle, and with the number of 
cycles fixed. This is used for welding in which the surrounding conditions 
vary to only a limited extent, such as an adaptability ratio of 1:2.5 
(.+-.40%), in which high reproducibility is required with only slight 
electrode deterioration (electrode wear is not compensated in this mode). 
This is effective in the case of processed plates (zincrometal etc.). 
It is always possible to introduce control of the current band and cos .0. 
independently of the mode used. In this respect, if an adaptive mode on 
the current constancy is used (3 or 4), any current abnormality, for 
example short-circuit welding, is difficult to detect as it automatically 
seeks to return it to its normal value. 
When usuing the ALU board, the apparatus allows type 1 rapid squeezing, 
with automatic recognition of when the plates are squeezed, so shortening 
squeezing and pressure times for all welding modes. 
The proposed adaptive welding control device is a device supplied at 110 
V/50 Hz, but also with a version for 115 V/60 Hz. 
Inside the apparatus, the only voltage which can be dangerous for the 
operator, should he come into contact with it, is the supply voltage, 
which follows a path through the mother board, the power supply board and 
the supply transformer. 
The user can also extend the distribution of the 110 V voltage by directly 
using the output contacts of the input/output board for controlling other 
apparatus operating at this voltage. A check should be made that the 
apparatus is not connected to the supply mains before beginning any 
maintenance work, and especially before extracting or inserting a board. 
If this is not done, then damage to the electronic parts can result. 
It should be noted that the power voltage of the welding transformer 
primary in no case enters inside the welding control unit. 
From the software aspect, each program executed can be divided into two 
parts, namely the main part and the dialogue part. 
Such a division is logical. This is because when one part is operating, the 
other cannot operate and vice versa. Each of these two parts comprises 
modules with interrupts and restarts, i.e. non-synchronous events which 
can interrupt the progress of that part being executed, in order to 
execute a certain function, and then restart the interrupted program 
without varying the conditions existing at the moment of the interruption. 
The main part is that which is connected both to the dialogue part and to 
the actual subroutines of the system. It is composed of: (1) the main 
welding program; (2) the installation module; (3) a collection of all the 
subroutines which can be recalled by all the modules with the exception of 
the dialogue part; and (4) the module which describes the mode of 
operation. 
The dialogue part comprises: 
(1) the module which contains and describes all the fields of the 16 
programs which can or cannot be set, and 
(2) the module which contains the messages to be displayed in ASCII code. 
It should be noted that the basic version comprises the software couplings 
for inserting the software module containing the adaptive programs 
relative to modes 1, 2, 3, 4, memorized in the ALU board, and for 
inserting the software module relative to the conversation with the 
computer processor or printer, as contained in the CI board. 
The 16 available programs can be divided into two groups in relation to the 
type of welding which has to be carried out. 
(a) The first group is constituted by the first 12 programs, used for 
welding operations on standard material, however all 16 programs can if 
necessary be used in standard mode. 
(b) The second group is constituted by programs 13 to 16, which are used 
for welding operations on special materials. They give the possibility of 
executing thermal cycles with a maximum of six special pulses, each of 
variable form. 
The messages which appear on the display unit can be divided into two 
categories: 
messages which appear during the writing of the program and during its 
reading, and can be set by the operator; 
messages which appear only during the reading of the program, and indicate 
values measured during the program execution.