Note: Descriptions are shown in the official language in which they were submitted.
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
TWO STAGE WELDER AND
METHOD OF OPERATING SAME
The invention relates to the art of electric arc welding and more particularly
to an electric
arc welder having two stage or two mode operation and the method performed by
this two stage
electric arc welder.
INCORPORATION BY REFERENCE
As background information, prior pending application Serial No. 866,358 filed
on May
29, 2001 together with references incorporated by reference in that
application are hereby
incorporated by reference. I~awai 4,889,969 shows a switch to shift between
DIP welding and
pulse welding and is incorporated by reference as background technology.
BACKGROUND OF INVENTION
Electric arc welders of the GMAW type are often powered by a high speed
switching
power supply or power source with a controller for controlling the current
waveform of the
welding process. The Lincoln Electric Company of Cleveland, Ohio has pioneered
the concept
of an electric arc welder with a wave shaper to control the shape of the
current waveform during
each cycle by the use of high frequency current pulses, the magnitude of each
pulse being
controlled by a pulse width modulator. In such welders, the wave shape of the
current is
accurately controlled to perform such diverse welding processes as pulse
welding, constant
voltage welding , spray welding, pulse welding, short-arc CV welding and STT
welding. In such
processes, the wave shape for each weld cycle is controlled by the pulse width
modulator to
produce a series of welding cycles that perform a designated process. Such arc
welders are quite
versatile; however, they are operated in selected mode by controlling the
pulses created by the
waveform shaper.
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
THE INVENTION
The present invention relates to an electric arc welder, of the type mentioned
above,
where the controller is shifted between two separate and distinct welding
processes or welding
modes. In accordance with the invention, the pulse shaper or pulse generator
shapes a series of
pulses forming a first welding process. The controller is shiftable to then
perform a second
welding process by implementing a series of different pulse shapes
constituting a different mode
of operation. By counting the cycles in the first mode of operation, the first
process is terminated
and the second process is initiated. Thereafter, the cycles of the next
process are counted until
they reach a set number, which indicates that the welder is to be shifted back
to the first welding
process. Thus, the electric arc welder has the capability of performing two
separate welding
processes by switching the controller from one mode of operation to another
mode of operation.
By this unique two stage or two state operation of an electric arc welder, the
welder can perform
a welding operation alternately using a first process and then a second
process. For instance, a
high energy process is performed for a short time and then the welder is
converted to a low
energy weld process. If the two processes are STT, low energy STT cycles are
implemented
followed by implementation of high energy STT cycles. Thus, in one embodiment,
the first
process is a high energy process and the second is a low energy process. A
counted number of
cycles of each process are used in the welding process to perform a total
welding operation by
implementing in series the first and second welding processes. As an example,
in one specific
embodiment the first process is a constant voltage spray process with high
heat. The second
process is a pulsed GMAW or low heat welding process. In the welding
operation, the controller
first implements the first process for a number of cycles and then the second
process for a
number of cycles. In another embodiment of the invention, the first process is
a pulse welding
-2-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
process where the pulses have high energy or high heat. This is used in
sequence with a low heat
STT weld process for a number of cycles. By alternating between the pulse
cycles and the STT
cycles, a desired total welding operation is performed. In another embodiment,
the first process
is a pulse welding process having high heat. This process is alternated with a
second weld
process, which is a short-arc, constant voltage welding process. In a still
further embodiment,
the first weld process is a pulse process for high heat. The second weld
process is a series of
pulses where the energy of the pulses are determined by a closed loop feedback
of the power
exerted. A still further example of the invention is an embodiment where the
first series of pulses
in the pulse welding operation are electrode positive to give high heat. The
second series of
pulses is a pulse welding process are negative, comprising electrode constant
voltage pulses.
By shifting between these welding processes, the actual welding operation is
controlled to
optimize the performance of the welder.
In accordance with still another aspect of the invention, the first weld
process of this two
stage or two state electric arc welder is a pulse welding process. This
process is continued until
the arc voltage indicates a short circuit. Then, the two stage welder is
shifted to a short clearing
weld process, such as an STT weld cycle. In the preferred embodiment, the
signal to shift from
the pulse welding process is not only dependent upon the indication of a short
by a plunge in the
arc voltage, but also on the time of a timer. The arc welder control shifts
from the first weld
process of the pulse mode into a short clearing process only when the short is
sustained for a set
time. The timer is preferably set to indicate that the short is maintained for
at least 1.0 ms and
preferably greater than a set time in the range of at least 0.2 to 0.5 ms.
Consequently, only when
there is an actual short, instead of an incipient short, does the electric arc
welder shift into the
second weld process for clearing the detected short circuit.
-3-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
In accordance with the present invention there is provided an electric arc
welder including
a high speed switching power supply with a controller for creating a first and
second weld
process across the gap between a workpiece and a welding wire advancing toward
the workpiece.
The first process uses a first current waveform and the second process uses a
second current
waveform. A circuit is used to shift between the first and second weld
processes, wherein the
circuit includes a counter for counting the waveforms in the first and second
processes. The
welder shifts from the process being processed to the other weld process when
the waveform
count of the weld process being processed reaches a preselected number for
each weld process.
By using this two stage welder, the arc welder can be shifted between two
separate and distinct
welding processes in accordance with the count or other parameter
In accordance with another aspect of the invention, there is a two stage arc
welder of the
type including a high speed switching power supply with a controller for
creating a pulse wave
weld process and a weld process to clear a detected short. A circuit is
activated to create a short
signal when the arc voltage is below a value indicative of a short and there
is a switch to shift the
controller from the pulse wave process to the short clearing process by a
process shift signal
created upon creation of the short signal. In an aspect of the invention, the
two stage welder
includes a timer to create the shift signal only when the short signal is held
for a given time
which is defined as greater than about 1.0 ms and preferably greater than a
set time in the general
range of 0.2 to 0.5 ms. Consequently, when the short is maintained for a
preselected time, the
two stage welder is shifted from the pulse mode of operation to a short
clearing mode of
operation. In the preferred embodiment, the short clearing mode of operation
is an STT weld
process.
In accordance with yet a further aspect of the invention, there is provided a
method of
-4-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
operating an electric arc welder of the type including a high speed switching
power supply with
a controller. This controller creates a first and second weld process across a
gap between the
workpiece and the welding wire advancing toward the workpiece by a wire
feeder. The first
process of the method has a first current waveform. The second process has a
second waveform.
The method comprises shifting between the first and second weld processes and
is implemented
by counting the waveforms in the first and second processes. The weld process
being performed
is shifted to the other process when the waveform count of the process being
performed reaches
a selected number. In a further aspect of the present invention there is a
provision of a method
of operating an electric arc welder including a high speed switch and power
supply with a
controller for creating a pulse wave process and a short clearing weld
process. The method
comprises creating a short signal when the arc voltage is below a value
indicative of a short and
then shifting the controller from the pulse wave process to the short clearing
process by a shift
signal created upon detection of the short circuit. In this method, the shift
signal is created only
when the short signal is held for a given time which in practice is less than
1.0 ms and actually
in the general range of 0.20-0.50 ms.
The primary object of the present invention is the provision of a two stage
electric arc
welder that alternately performs two welding processes during a single welding
operation.
Yet another object of the present invention is the provision of a two stage
arc welder, as
defined above, which arc welder has a counter to count the cycles of one
process to determine
when there is to be a shift in the process being performed by the welder.
Still a further object of the present invention is the provision of a two
stage arc welder,
as defined above, which two stage arc welder performs a pulse welding process
until a non-
incipient short is detected. Then, the two stage welder is shifted into a
second mode of operation
-5-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
for clearing the short.
Another object of the present invention is the provision of a method of
operating a two
stage arc welder, as defined above.
Still a further object ofthe present invention is the operation of a two stage
arc welder,
as defined above, which two stages involve one of many combinations of a
distinct first welding
process and a distinct, different second welding process. The two processes
alternate back and
forth during a single welding operation.
These and other objects and advantages will become apparent from the following
description taken together with the accompanying drawings.
~ , BRIEF DESCRIPTION OF DRAWINGS
FIGURE 1 is a combined block and wiring diagram illustrating the preferred
embodiment
of the two stage arc welder of the present invention;
FIGURE 2 is a flow chart in block diagram format of a method and operation for
the two
stage arc welder, whereby a detected non-incipient short shifts the welding
process being
performed;
FIGURE 3 is a flow chart in block diagram format showing a further
implementation of
the two stage welder, constructed in accordance with the present invention;
and,
FIGURE 4 is a current graph illustrating the operation of the two stage welder
in
accordance with the implementation of the invention illustrated in FIGURE 3.
PREFERRED EMBODIMENTS
Referring now to the drawings, wherein the showings are for the purpose of
illustrating
a preferred embodiment of the invention only and not for the purpose of
limiting same, FIGURE
1 shows a novel two stage welder A with a power source 10 comprising a high
speed switching
-6-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
power supply illustrated as inverter 12 having a three phase power supply
input 14 converted by
rectifier 16 into a DC rail in lines 20, 22. Output winding 30 of inverter 12
is the primary
winding of transformer T having a secondary winding 32 for supplying current
to a rectifier
network 40. This network provides a current level through positive lead 42 and
negative lead
44. A standard small inductor 50 is connected to a standard contact tip 54,
through which passes
a welding wire 60 that forms electrode E spaced from workpiece W to define an
arc gap through
which the current is passed during the arc welding process. Welder A performs
many types of
electric arc welding by passing a current of a preselected shape across the
gap between electrode
E and workpiece W. As the arc melts wire 60 and workpiece W to perform a
welding operation,
wire feeder 100 pulls wire from reel 102 at a speed (WFS) determined by the
rotational speed of
motor 104. This speed is read by a feedback tachometer 110 and is controlled
by the input
voltage to pulse width modulator 112 from the output of error amplifier 114.
This amplifier has
a first input 120 which is the voltage representing the desired wire feed
speed (WFS). This speed
may be controlled by an analog circuit or more appropriately from a look-up
table from wave
shaper 180. The input voltage 120 determines the speed of motor 104, which
actual speed is
monitored by tachometer 110 for comparison with the voltage on line 120. The
actual speed
feedback is the voltage on input line 122. In this manner, the wire feed speed
is coordinated with
the weld process being implemented by welder A. The current wave shape across
electrode E
and workpiece W is determined by software controller 13 0 of the type
including a software pulse
width modulator 132 for generating a voltage on output control line 134 at a.
pulse rate
determined by the set frequency of oscillator 136. In this manner, the high
frequency pulses on
line 134 are controlled by the voltage on line 140, which voltage is the
output of a second error
amplifier 150 having a first input controlled by current detecting or sensing
shunt 152. The
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
voltage on line 154 is representative ofthe arc current ofthe welding process.
A command signal
on line 160 is compared to the actual arc current represented by the voltage
on line 154 to cause
the pulse width modulator 152 to follow the desired wave shape from wave
shaper or generator
180 by way of command line 160. The wire feed speed to error amplifier 114 is
also directed
from the wave shaper or generator. The generator 180 is of the synergistic
type so that both the
command signal 160 and the wire feed speed signal or voltage (WFS) on line 120
are
coordinated.
In accordance with the novel aspect of welder A, there is provided a switch
190 which,
in practice, is a software switch having a first position 192 and a second
position 194, as shown
~in FIGURE 1. When in position 192, wave shaper 180 is controlled in
accordance with a first
vProcess A from process control system 200 for Process A. In this manner,
process control system
200 is connected to the synergistic wave shaper 180 to implement Process A
from the wave
shaper 80 by way of controller 130. In a like manner, when switch 190 is in
position 1,94,
process control system 202 causes wave shaper 180 to implement the second
Process B by way
of the signal on command line 160. Thus, by shifting switch 190 between
positions 192, 194,
two separate welding processes are performed by welder A. Of course, it is
within the present
invention to have switch 190 with more than two positions so that the welder
can process in
sequence or in series more than two welding processes, if such operation is
desired. In practice,
it is preferred that only two separate weld processes be performed alternately
by welder A. In
accordance with another aspect of the invention, the position of switch 190 is
controlled by logic
on dashed line 210 from the output of cycle counter 212. The counter counts
each cycle during
either Process A or Process B. At the end of the count, as set by count
selector 214 or count
selector 216, the logic on line 210 shifts switch 190 into the other position
for implementing the
-g_
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
other weld process. Counter 212 counts to a number CA and then shifts to
Process B which is
maintained until the counter counts to a number CB. Then, switch 190 shifts
back to the first
process, i.e. Process A. In the preferred embodiment, one of the processes is
a high heat process
and the other is a low process. The numbers CA and CB are essentially the
same. Thus, the
welding operation involves a low heat portion and high heat portion which are
repeatedly
implemented during the total welding process to control the performance of the
welding
operation whether it is STT, pulse or otherwise. As will be shown, various
weld processes can
be alternately selected by a counter. Indeed, the welder A can be interactive
so that the shift from
one process to the other is determined by parameters as distinguished from
count numbers. For
instance, the voltage sensor 170 produces a voltage on 172 that detects a
short, which is used in
FIGURE 2 for transition between the first Process A and the second Process B
wherein the
second process is an arc clearing process. The counts can be drastically
different and the
interactive parameters can be selected to shift into a preselected process
after a given process
transitions into a detectable weld condition.
In practice, Process A is normally a high energy process and Process B is a
low energy
process. The count numbers CA and CB are essentially the same. To change the
welding
operation, number CA is increased or number CB is decreased to increase the
heat during the
welding operation. In a like manner, to decrease the heat, the number CA is
decreased or the
number CB is increased. ~f course, combinations of these increases or
decreases could be used
in selecting the desired total heat during a welding operation. In a preferred
embodiment, Process
A and Process B are the same, but with different size waveforms. It may be
pulse welding or
STT welding. However, in accordance with the invention, the processes could be
completely
diverse. For instance, in practice, Process A is a constant voltage spray
process with high heat
-9-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
and Process B is a pulsed GMAW low heat. Counter 212 is set by count selectors
214, 216 to
the desired total heat for the welding operation. In practice, Process A is a
pulse welding process
with high heat whereas Process B is an STT weld process with a lower wire feed
speed. Also,
in practice Process A is a pulse welding process with higher heat and Process
B is a short-arc
constant voltage process. A still further implementation of the present
invention Process A is
a pulse welding process and Process B is a closed loop control process, such
as a process wherein
the current is controlled by the output power. Yet a further implementation of
the present
invention is where Process A is a pulse electrode positive and Process B is an
electrode negative
constant voltage weld process. In that implementation of the present
invention, a polarity switch
is added in the output circuit before inductor 50, which polarity circuit is
shifted at the same time
as switch 190. Other implementations of the present invention involve various
combinations of
welding process to perform the desired overall weld operation.
An interactive control system 220 is schematically illustrated in FIGURE 2,
wherein the
wave shaper generator and control 222 creates the voltage on control line 134,
as previously
described. Control 130 is in block 222. The voltage controls power supply 12
which is
monitored by a process control network 224 together with the voltage on line
172 from voltage
sensor 170, shown in FIGURE 1. Timer 226 of the process control network is set
to a time
generally greater than about 1.0 ms and preferably greater than a set time in
the general range of
0.2-0.5 ms. The output from the timer network is a logic on line 232 directed
to a decision block
230 to decide whether or not there is a short circuit that has been detected
for a time greater than
the time set of time 226. The position of switch 190 is controlled by decision
block 230. When
there is a short that exceeds the set time of timer 226, switch 190 is shifted
into position 194.
Thus, when there is a long term non-incipient short; switch 190 shifts to the
alternate position
-10-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
194 to implement the second weld process. In this implementation of the
present invention, the
first process is a pulse wave form controlled in accordance with the wave
shape determined by
a system shown as block 240. Block 242 represents a system to create an STT
wave form or
other short clearing weld process. System 220 performs the first mode of
operation defined,as
a pulse wave form controlled by the system represented by block 240. Whenever
there is a short,
the voltage on line 172 drops down below a threshold. This determines a short
circuit. Such
detected condition is timed by timer 226. If the time of the short exceeds the
set time of the
timer, the logic on line 232 indicates to the decision block that there is a
non-incipient actual
short circuit. This logic immediately shifts the software switch 190 to the
arc clearing weld
process, indicated as an STT process. When the short is cleared in accordance
with the short
clearing process, the voltage on line 172 immediately shifts to a plasma level
or arc voltage. This
is above the threshold and causes decision block 230 to shift switch 190 into
position 192 for
implementation of the pulse wave form controlled by the system represented by
block 240.
Consequently, system 220 does not involve a cycle counter, but senses a
welding parameter for
actual shifting of the weld process from one weld process to the other. This
happens rapidly and
occurs whenever the selected parameter is detected.
In FIGURES 3 and 4, system 250 includes a low heat weld process represented by
block
260. Process A is a low heat STT weld process. In a like manner, a high heat
STT weld process
is represented by block 262. Counter 212 causes first STT pulses 260a to be
processed as shown
in FIGURE 4. After the desired number of STT pulses 260a have been counted by
cycle counter
212, switch 190 is shifted into position 194 by the logic on line 210. This
generates the large,
or high heat, STT pulses 262a, as shown in FIGURE 4. These high heat pulses
are counted in
accordance with the selected number for counter 212. In this manner, the
number of waveforms
-11-
CA 02474938 2004-07-30
WO 03/076114 PCT/US03/00320
or cycles of low and high STT is adjusted to determine the total heat during a
welding operation.
The invention involves a two or more stage welder which implements in sequence
distinctly different welding processes. Preferably, the duration of these
processes is determined
by a counter; however, a parameter can be used for shifting between the weld
processes. Only
representative processes have been discussed and other weld processes can be
used when
implementing the invention.
-12-
