Note: Descriptions are shown in the official language in which they were submitted.
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METHOD TO CONTROL AN ARC WELDING SYSTEM TO REDUCE SPA! _______ IER
[0001] This U.S. Patent Application Claims priority to and the benefit of U.S.
Provisional Patent
Application serial number 61/405,895 filed on October 22, 2010, which is
incorporated herein by
reference in its entirety.
[0002] This U.S. Patent Application Claims priority to and the benefit of U.S.
Provisional Patent
Application serial number 61/413,007 filed on November 12, 2010, which is
incorporated herein
by reference in its entirety.
[0003] The preferred embodiment section and the drawings of U.S. Patent No.
7,304,269 issued
on December 4, 2007 are incorporated by reference herein.
TECHNICAL HUD
[0004] Certain embodiments relate to pulsed electric arc welding equipment and
processes.
More particularly, certain embodiments relate to anticipating or reacting to
short circuits formed
between a welding electrode and a workpiece during a pulsed electric arc
welding process by
reducing the Output current during the time of the short to reduce spatter.
BACKGROUND
[0005] In electric arc welding, a popular welding process is pulse welding
which primarily uses
a solid wire electrode with an outer shielding gas. MIG welding uses spaced
pulses which first
melt the end of an advancing wire electrode and then propels the molten metal
from the end of
the wire through the arc to the workpiece. A globular mass of molten metal is
transferred during
each pulse period of the pulse welding process. During certain pulse periods,
especially in
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CONFIRMATION COPY
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applications where the welding electrode operates very close to the workpiece,
molten metal
contacts the workpiece before being entirely released from the advancing wire
electrode. This
creates a short circuit (a.k.a., a short) between the advancing wire electrode
and the workpiece.
It is desirable to eliminate or clear the short rapidly to obtain the
consistency associated with
proper pulse welding. However, clearing a short can result in undesirable
spatter being gen-
erated. Such spatter causes inefficiencies in the welding process and can
result in molten metal
being spattered over the workpiece which may have to be removed later using a
grinding tool,
for example.
[0006] Further limitations and disadvantages of conventional, traditional, and
proposed ap-
proaches will become apparent to one of skill in the art, through comparison
of such ap-
proaches with embodiments of the present invention as set forth in the
remainder of the pre-
sent application with reference to the drawings.
BRIEF SUMMARY
[0007] Embodiments of the present invention comprise an electric arc welding
System and
methods for reducing spatter during a pulsed electric arc welding process.
Spatter is reduced
during a welding Operation by reducing the welding Output current during a
time when a short
occurs between the welding electrode and the workpiece. In one embodiment, a
switching
module, including an electrical switch and a resistive path, is incorporated
into the return
welding current path of a power source of the electric arc welding System.
During non-shorting
conditions of the pulse welding Operation, the electrical switch is closed or
on, allowing welding
current to freely return to the power source by experiencing minimal
resistance through the
switch. However, when a short is anticipated or occurs during the welding
process, the electrical
switch is opened or turned off, forcing the welding current to have to go
through the resistive
path of the switching module, causing the level of the welding current to be
lower than it
otherwise would be. The lower current generated during the short interval
results in less spatter
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being created when the short is cleared. The time of occurrence of a short
during the pulse
periods may be tracked and a blanking interval, overlapping the interval of
time corresponding to
an anticipated short, may be applied such that the switch is open during the
blanking interval.
[0008] These and other features of the claimed invention, as well as details
of illustrated em-
bodiments thereof, will be more fully understood from the following
description and draw-
ings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Fig. 1 illustrates a block diagram of an example embodiment of an
electric arc welding
System incorporating a switching module in a welding current return path;
[0010] Fig. 2 illustrates a diagram of an example embodiment of a portion of
the System of Fig.
1, including the switching module in the welding current return path;
[0011] Fig. 3 illustrates a schematic diagram of an example embodiment of the
switching
module of Fig. 1 and Fig. 2;
[0012] Fig. 4 illustrates a flowchart of a first example embodiment of a
method for preventing
spatter in a pulsed electric arc welding process using the System of Fig. 1;
[0013] Fig. 5 illustrates an example of a conventional pulsed Output current
waveform resulting
from a conventional pulsed electric arc welder that does not use the switching
module of Figs. 1-
3 in accordance with the method of Fig. 4;
[0014] Fig. 6 illustrates the exploding spatter process discovered using high
speed video
technology in a free-flight transfer process having a tethered connection;
[0015] Fig. 7 illustrates an example of a pulsed Output current waveform
resulting from the
pulsed electric arc welder of Fig. 1 that does use the switching module of
Figs. 1-3 in accordance
with the method of Fig. 4;
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[0016] Fig. 8 illustrates a flowchart of another example embodiment of a
method for preventing
spatter in a pulsed electric arc welding process using the system of Fig. 1;
and
[0017] Fig. 9 illustrates an example of a pulsed Output current waveform
resulting from the
pulsed electric arc weider of Fig. 1 that uses the switching module of Figs. 1-
3 in accordance
with the method of Fig. 8.
DETAILED DESCRIPTION
[0018] During an arc-welding process, when the distance between the tip of the
electrode and the
workpiece is relatively small, molten metal may be transferred via a contact
transfer process
(e.g., a surface-tension-transfer or STT process) or a free-flight transfer
process (e.g., a pulsed
welding process) with a tethered connection. In a contact transfer process, a
molten metal ball
on the tip of the welding electrode makes contact with the workpiece (i.e.,
shorts) and Starts to
"wet into" the molten puddle on the workpiece before the molten metal ball
begins to sub-
stantially separate from the tip of the electrode.
[0019] In a free-flight transfer process, the molten metal ball breaks free of
the tip of the
electrode and "flies" across the arc toward the workpiece. However, when the
distance between
the tip of the electrode and the workpiece is relatively short, the molten
metal ball flying across
the arc can make contact with the workpiece (i.e., short) while a thin tether
of molten metal still
connects the molten metal ball to the tip of the electrode. In such a tethered
free-flight transfer
scenario, the thin tether of molten metal tends to explode, causing spatter,
when the molten metal
ball makes contact with the workpiece as illustrated in Fig. 6 herein, due to
a rapid increase in
current through the tether.
[0020] Fig. 1 illustrates a block diagram of an example embodiment of an
electric arc welding
System 100 incorporating a switching module 110 in a welding Output return
path and providing
welding Outputs 121 and 122. The System 100 includes a power Converter 120
capable of
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converting an input power to a welding output power. The power Converter 120
may be an in-
verter-type power Converter or a chopper-type power Converter, for example.
The System 100
further includes a wire feeder 130 capable of feeding a welding electrode wire
E through, for
example, a welding gun (not shown) that connects the welding electrode wire E
to the welding
Output 121.
100211 The System 100 also includes a current shunt 140 operatively connected
between the
power Converter 120 and the welding Output 121 for feeding welding Output
current to a current
feedback sensor 150 of the System 100 to sense the welding Output current
produced by the
power Converter 120. The System 100 further includes a voltage feedback sensor
160 operatively
connected between the welding Output 121 and the welding Output 122 for
sensing the welding
Output voltage produced by the power Converter 120. As an alternative, the
switching module
110 could be incorporated in the outgoing welding current path, for example,
between the power
Converter 120 and the current shunt 140, or between the current shunt 140 and
the welding
Output 121.
[0022] The System 100 also includes a high-speed Controller 170 operatively
connected to the
current feedback sensor 150 and the voltage feedback sensor 160 to receive
sensed current and
voltage in the form of Signals 161 and 162 being representative of the welding
Output. The
System 100 further includes a waveform generator 180 operatively connected to
the high speed
Controller 170 to receive command Signals 171 from the high speed Controller
170 that tell the
waveform generator how to adapt the welding waveform signal 181 in real time.
The waveform
generator 180 produces an Output welding waveform signal 181 and the power
Converter 120 is
operatively connected to the waveform generator 180 to receive the Output
welding waveform
signal 181. The power Converter 120 generates a modulated welding Output
(e.g., voltage and
current) by Converting an input power to a welding Output power based on the
Output welding
waveform signal 181.
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[0023] The switching module 110 is operatively connected between the power
Converter 120 and
the welding Output 122 which is connected to the welding workpiece W during
Operation. The
high speed Controller 170 is also operatively connected to the switching
module 110 to provide a
switching command signal (or a blanking signal) 172 to the switching module
110. The high
speed Controller 170 may include logic circuitry, a programmable
microprocessor, and Computer
memory, in accordance with an embodiment of the present invention.
[0024] In accordance with an embodiment of the present invention, the high-
speed Controller
170 may use the sensed voltage signal 161, the sensed current signal 162, or a
combination of the
two to determine when a short occurs between the advancing electrode E and the
workpiece W,
when a short is about to clear, and when the short has actually cleared,
during each pulse period.
Such schemes of determining when a short occurs and when the short clears are
well known in
the art, and are described, for example, in U.S. 7,304,269, portions of which
are incorporated
herein by reference. The high-speed Controller 170 may command the waveform
generator 180
to modify the waveform signal 181 when the short occurs and/or when the short
is cleared. For
example, when a short is determined to have been cleared, the high-speed
Controller 170 may
command the waveform generator 180 to incorporate a plasma boost pulse (see
pulse 750 of Fig.
7) in the waveform signal 181 to prevent another short from occurring
immediately after the
Clearing of the previous short.
[0025] Fig. 2 illustrates a diagram of an example embodiment of a portion of
the System 100 of
Fig. 1, including the switching module 110 in the welding current return path.
The power
Converter 120 may include an inverter power source 123 and a freewheeling
diode 124. The
welding Output path will have an inherent welding circuit inductance 210 due
to the various
electrical components within the welding Output path. The switching module 110
is shown as
having an electrical switch 111 (e.g., a power transistor circuit) in parallel
with a resistive path
112 (e.g., a network of high power rated resistors).
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[0026] During a pulse period of the welding waveform, when no short is
present, the electrical
switch 111 is commanded to be closed by the switching command signal 172 from
the high-
speed Controller 170. When the electrical switch 111 is closed, the electrical
switch 111 provides
a very low resistance path in the Output welding return path, allowing welding
current to freely
return to the power Converter 120 through the switch 111. The resistive path
112 is still present
in the welding Output return path, but most of the current will flow through
the low resistance
path provided by the closed switch 111. However, when a short is detected, the
electrical switch
111 is commanded to be opened by the switching command signal 172 from the
high-speed
Controller 170. When the electrical switch 111 is opened, current is cut off
from flowing through
the switch 111 and is forced to flow through the resistive path 112, resulting
in the level of the
current being reduced due to the resistance provided by the resistive path
112.
[0027] Fig. 3 illustrates a schematic diagram of an example embodiment of the
switching
module 110 of Fig. 1 and Fig. 2. The switching module 110 includes the
transistor circuit 111
and the resistor network 112 as shown. The switching module 110 may include a
circuit board
for mounting the various electrical components of the module 110 including the
transistor circuit
111, the resistor network 112, LEDs, and Status logic circuitry, for example.
[0028] Fig. 4 illustrates a flowchart of a first example embodiment of a
method 400 for pre-
venting spatter in a pulsed electric arc welding process using the System 100
of Fig. 1. Step 410
represents Operation where the switch 111 of the switching module 110 is
normally closed (no
short condition). In Step 420, if a short is not detected, then the switch 111
remains closed (no
short condition). However, if a short is detected then, in step 430, the
switch 111 is com-
manded to go through an opening and closing sequence during the short interval
(i.e., the time
period over which the electrode is shorted to the workpiece).
[0029] The opening/closing sequence in step 430 Starts by opening the switch
111 when the
short is first detected. The switch 111 remains open for a first period of
time (e.g., a first 10% of
the short interval). This decreases the Output current quickly so the short
does not break right
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away causing a large amount of spatter. After the first period of time, the
switch is again closed
and the Output current is ramped during a second period of time to cause the
molten short to
begin to form a narrow neck in an attempt to break free from the electrode and
clear the short.
During this second period of time, as the current is ramping, a dv/dt
detection scheme is per-
formed to anticipate when the short will clear (i.e., when the neck will
break). Such a dv/dt
scheme is well known in the art. The switch 111 is then opened again just
before the short is
about to clear (e.g., during the last 10% of the short interval) in order to
quickly lower the Output
current once again to prevent excessive spattering when the neck actually
breaks (i.e., when the
short actually clears).
[0030] In step 440, if the short (short between the electrode and the
workpiece) is still present,
then the switch 111 remains open. However, if the short has been cleared then,
in step 450, the
switch 111 is again closed. In this manner, during a short condition, the
switch 111 goes through
an opening/closing sequence and the current flowing through the welding Output
path is reduced
when the switch is open, resulting in reduced spatter. The method 400 is
implemented in the
high-speed Controller 170, in accordance with an embodiment of the present
invention. Fur-
thermore, in accordance with an embodiment of the present invention, the
System 100 is able to
react at a rate of 120 kHz (i.e., the switching module 110 can be switched on
and off at this
high rate), providing sufficient reaction to detection of a short and
detection of the Clearing of the
short to implement the method 400 in an effective manner.
[0031] In accordance with a somewhat simpler alternative embodiment, instead
of going through
the opening/closing sequence described above with respect to Fig. 4, the
current of the welding
circuit path is decreased, in response to detection of a short between the
advancing wire electrode
and the workpiece, by opening the switch 111 for at least a determined period
of time, thus
increasing the resistance in the welding circuit path. For most pulse periods,
the determined
period of time is of a duration allowing for the short to clear without having
to first increase the
current of the welding circuit path. During a given pulse period, if the short
clears before the
determined period of time has expired as desired, then the process proceeds to
the next part of
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the pulse period. However, if the short does not clear within the
predetermined period of time
then, immediately after the determined period of time, the switch 111 is
closed again, causing the
current of the welding circuit path to once again increase and clear the
short. In such an
alternative embodiment, the switch 111 is simply opened for at least part of
the determined
period of time in response to the detection of the short. In most pulse
periods, the current does
not have to be increased to clear the short.
[0032] Furthermore as an Option, when the short between the advancing wire
electrode and the
workpiece is detected, a speed of the advancing wire electrode can be slowed.
Slowing the speed
of the advancing wire electrode helps to clear the short more readily by not
adding as much
material to the short as otherwise would be added. To slow the speed of the
advancing wire
electrode, a motor of a wire feeder advancing the wire electrode may be
switched off and a brake
may be applied to the motor. The brake may be a mechanical brake or an
electrical brake, in ac-
cordance with various embodiments.
[0033] Fig. 5 illustrates an example of a conventional pulsed Output current
waveform 500
resulting from a conventional pulsed electric arc weider that does not use the
switching module
110 of Figs. 1-3 in accordance with the method 400 of Fig. 4, or the simpler
alternative method
described above. As can be seen from the waveform 500 of Fig. 5, after a peak
pulse 510 is
fired, a short may occur starting at time 520, for example, that lasts until
time 530, for example,
when the short is cleared The times 520 and 530 define a short interval 540.
As can be seen in
Fig. 5, peak pulses 510 are fired at regular intervals during the multiple
pulse periods or cycles of
the welding process. During any given cycle or pulse period, a short condition
may or may not
occur. In a conventional System, when a short occurs, there is very little
resistance in the
welding Output path compared to the inductance. Current continues to flow even
if the power
source is turned off.
[0034] Referring again to Fig. 5, during the short interval 540, the Output
current tends to
increase due to the lack of an arc between the electrode E and the workpiece W
(the resistance
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becomes very low), and due to the fact that the welding circuit inductance 210
acts to keep
current flowing in the welding Output path, even when the power Converter 120
is phased back to
a minimum level. The current tends to increase until the short is cleared
(i.e., until the molten
metal short breaks free of the electrode E). However, at such increased
current levels, when the
short breaks or clears, the increased current levels tend to cause the molten
metal to explode
causing spatter.
[0035] Fig. 6 illustrates the exploding spatter process that was discovered
using high speed video
technology in a free-flight transfer process having a tethered connection. A
high peak pulse
(e.g., 510) causes a ball of molten metal 610 to push out towards the
workpiece W creating a
narrow tether 620 between the ball 610 and the electrode E. As the ball 610
flies toward the
workpiece W across the arc, the tether 620 narrows and, eventually, a short
occurs between the
electrode E and the workpiece W through the tether 620. This condition tends
to occur for
almost every pulse period in an Operation where the welding electrode operates
very close to the
workpiece. In particular, it was discovered that for a free-flight transfer
pulse welding process,
the tether 620 creates an incipient short and a large amount of current can
begin to flow through
the narrow tether 620. The increasing current level finally causes the
relatively thin molten
tether 620 to explode creating spatter 630 as shown in Fig. 6. However, by
incorporating the
switching module 110 and the method 400 (or the simpler alternative) as
described above herein,
the spatter 630 that is created can be greatly reduced.
[0036] Fig. 7 illustrates an example of a pulsed Output current waveform 700
resulting from the
pulsed electric arc weider 100 of Fig. 1 that uses the switching module 110 of
Figs. 1-3 in ac-
cordance with the method 400 of Fig. 4. As can be seen from the waveform 700
of Fig. 7,
after a peak pulse 710 is fired, a short may occur starting at time 720, for
example, that lasts until
time 730, for example, when the short is cleared. The times 720 and 730 define
a short interval
740. As can be seen in Fig. 7, peak pulses 710 are fired at regular intervals
during the multiple
pulse periods or cycles of the welding process. During any given cycle, a
short condition may or
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may not occur. However, when the distance between the tip of the electrode and
the workpiece
is relatively small, a short can occur on almost every cycle.
[0037] Referring again to Fig. 7, during the short interval 740, the switch
111 of the switching
module 110 is opened when the short first occurs and again when the short is
about to clear,
causing the Output current to flow through the resistive path 112 and,
therefore, causing the
current level to reduce. As an example, the switching signal 172 may be a
logic signal that goes
from high to low when a short is detected, causing the switch to open.
Similarly, when the short
is cleared, the switching signal 172 may go from low to high to close the
switch 111 again.
When the switch 111 is opened, the resistive path 112 puts a load on the
welding Output path
allowing the freewheeling current to drop quickly to desired levels. The
current tends to reduce
until the short is cleared and, at such reduced current levels, when the short
breaks or clears, the
molten metal tends to pinch off in an unexplosive manner, eliminating or at
least reducing the
amount of spatter created. Also, in the waveform 700 of Fig. 7, the plasma
boost pulse 750,
which is used to help prevent another short from occurring immediately after
the short that was
just cleared, is more prominent and potentially more effective.
[0038] Fig. 8 illustrates a flowchart of another example embodiment of a
method 800 for pre-
venting spatter in a pulsed electric arc welding process using the System 100
of Fig. 1. In accor-
dance with an embodiment, the method 800 is performed by the Controller 170.
The high-speed
Controller 170 tracks the times of occurrence of the shorts and/or the
Clearing of the shorts and
provides an estimate of when the short interval 940 (the time between the
occurrence of a short
and when the short is cleared) (see Fig. 9) will occur during at least the
next pulse period. From
this estimate, a blanking interval 960 (see Fig. 9) can be determined which is
used to generate
the blanking signal 172.
[0039] In step 810 of the method 800, the System 100 detects the occurrence of
shorts and/or the
Clearing of those shorts during the repeating pulse periods of the pulsed
welding waveform, ac-
cording to known techniques. In step 820, the time of occurrence of the
detected shorts and/or
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Clearings within the pulse periods are tracked (e.g., by the high-speed
Controller 170). In step
830, the location and duration of the short interval 940 (see Fig. 9) for a
next pulse period is
estimated based on the tracking results. In step 840, an overlapping blanking
interval 960 for at
least the next pulse period is determined based on the estimated location of
the short interval for
the next pulse period. In step 850, a blanking signal (a type of switching
signal) 172 is generated
(e.g., by the Controller 170) to be applied to the switching module 110 during
the next pulse
period.
[0040] Fig. 9 illustrates an example of a pulsed Output current waveform 900
resulting from the
pulsed electric arc weider 100 of Fig. 1 that uses the switching module 110 of
Figs. 1-3 in ac-
cordance with the method 800 of Fig. 8. As can be seen from the waveform 900
of Fig. 9,
after a peak pulse 910 is fired, a short may occur starting at time 920, for
example, that lasts until
time 930, for example, when the short is cleared. The times 920 and 930 define
a short interval
940. As can be seen in Fig. 9, peak pulses 910 are fired at regular intervals
during the welding
process. During any given cycle, a short condition may or may not occur.
However, during a
welding process where the arc length is relatively short (i.e., where the wire
electrode is operated
relatively close to the workpiece), shorts can occur in almost every pulse
period.
[0041] In accordance with the method 800, the times of occurrence of the short
and/or clearing
of the short within the pulse period are determined and tracked from pulse
period to pulse period.
In this manner, the Controller 170 may estimate the location of the short
interval that will likely
occur in the next or upcoming pulse periods. However, at the beginning of a
pulsed welding
process, before any substantial tracking information is available, the
location of the short interval
may be a stored default location based on, for example, experimental data or
stored data from a
previous welding process. The blanking signal 172 can be adapted or modified
to form a
blanking interval 960 within the blanking signal 172 which temporally overlaps
the estimated
short interval 940 for the next pulse period(s). Ideally, the blanking
interval 960 Starts shortly
before the short interval 940 of the next pulse period (e.g., before the time
920) and ends shortly
after the short interval 940 of the next pulse period (e.g., after the time
930), thus the temporal
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overlap. In one embodiment, only the times of occurrence of a short are
tracked, not the Clearing
of the shorts. In such an embodiment, the duration of the blanking interval is
set to last long
enough for the short to clear, based on experimental knowledge.
[0042] In this manner, the actual occurrence of a short during the next pulse
period does not
have to be detected before the switch 111 of the switching module 110 can be
opened. As the
pulsed welding process progresses, the location of the short interval may
drift or change as the
distance between the wire electrode and the workpiece drifts or changes, for
example. However,
in this embodiment, since the location of the short interval is being tracked
over time, the
location of the blanking signal can be adapted to effectively follow and
anticipate the short
interval. By opening the switch 111 during the blanking interval 960, the
current drops and it is
expected that the tether will occur and break during the blanking interval
960.
[0043] Experimental results have shown that, using the switching module 110 as
described
herein in a particular pulsed welding scenario, the welding Output current
level at the point of
Clearing the short can be reduced from about 280 amps to about 40 amps, making
a tremendous
difference in the amount of spatter produced. In general, reducing the current
below 50 amps
seems to significantly reduce spatter. In addition, travel speeds (e.g., 60-80
inches/minute) and
deposition rates are able to be maintained.
[0044] Other means and methods of reducing the welding Output current level
during the time
period when a short is present between a welding electrode and a workpiece are
possible as well.
For example, in an alternative embodiment, the control topology of a welding
power source may
be configured to control the Output current to a highly regulated level during
the time of the
short. The power source can control the shorting current to a lower level
(e.g., below 50 amps)
during a shorting interval to reduce the spatter. For example, referring to
Fig. 1, the switching
module 110 can be disabled or eliminated, allowing current to freely flow in
the welding Output
circuit path. The Controller 170 is configured to command the waveform
generator 180 to
modify a portion of the Output welding waveform signal 181 of the welding
process during the
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blanking interval to reduce the welding Output current through the welding
Output circuit path.
Therefore, in this alternative embodiment, the Controller 170 reduces the
current during the
blanking interval through the waveform generator 180 and the power Converter
120, instead of
via the switching module 110. Such an alternative embodiment can work quite
well if the
inductance 210 of the welding circuit is sufficiently low.
[0045] In summary, an electric arc weider and a method for performing a pulse
welding process
producing reduced spatter are disclosed. The weider produces a current between
an advancing
electrode and a workpiece. The weider includes a short-detecting capability
for detecting a short
condition upon occurrence of a short circuit between the advancing electrode
and the workpiece.
The weider is controlled to reduce the current between the advancing electrode
and the
workpiece during the time of the short to reduce spatter of molten metal when
the short clears.
[0046] An embodiment of the present invention comprises a method for reducing
spatter in a
pulsed arc-welding process. The method includes tracking times of occurrence
of short intervals
during pulse periods of a pulsed arc-welding process using a Controller of a
welding System. The
tracking may be based on at least one of detecting occurrences of shorts
during pulse periods of
the pulsed welding process and detecting Clearing of shorts during pulse
periods of the pulsed
welding process. The method further includes estimating a temporal location of
a short interval
for at least a next pulse period of the pulse welding process based on the
tracking. The method
also includes determining a blanking interval for at least a next pulse period
based on the
estimating. The method may further include generating a blanking signal for at
least a next pulse
period based on the blanking interval. The method may further include
increasing a resistance of
a welding circuit path of the welding System during the blanking interval in
response to the
blanking signal to reduce a welding current through the welding circuit path
during the blanking
interval. Increasing the resistance may include opening an electrical switch
of a switching
module disposed in the welding circuit path. In accordance with an embodiment,
the electrical
switch is in parallel with a resistive path within the switching module. The
method may include
reducing a welding current through a welding circuit path of the welding
System during the
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blanking interval for at least a next pulse period by modifying a portion of a
waveform of the
welding process during the blanking interval, wherein the waveform is
generated by a waveform
generator of the welding System. In accordance with an embodiment, the
blanking interval is
temporally wider than and temporally overlaps an expected short interval of at
least a next pulsed
period.
[0047] An embodiment of the present invention comprises a System for reducing
spatter in a
pulsed arc-welding process. The System includes a Controller configured for
tracking times of
occurrence of short intervals during pulse periods of a pulsed arc-welding
process of a welding
System. The Controller is further configured for estimating a temporal
location of a short interval
for at least a next pulse period of the pulsed welding process based on the
tracking. The
Controller is also configured for determining a blanking interval for at least
a next pulse period
based on the estimating. The Controller may also be configured for generating
a blanking signal
for at least a next pulse period based on the blanking interval. In accordance
with an em-
bodiment, the blanking interval is temporally wider than and temporally
overlaps an expected
short interval of at least a next pulse period. The system may further include
a switching module
disposed in a welding circuit path of the welding system and operatively
connected to the
Controller. The switching module is configured to increase a resistance of the
welding circuit
path of the welding system during the blanking interval in response to the
blanking signal to
reduce a welding current through the welding circuit path during the blanking
interval. The
switching module includes an electrical switch and a resistive path in
parallel. The Controller
may be configured for commanding a waveform generator of the welding system to
reduce a
welding current through a welding circuit path of the welding system during
the blanking
interval for at least a next pulse period by modifying a portion of a waveform
of the welding
process during the blanking interval. The Controller may further be configured
to detect oc-
currences of shorts during pulse periods of the pulsed welding process, and to
detect occur-
rences of Clearing of shorts during pulse periods of the pulsed welding
process.
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[0048] An embodiment of the present invention comprises a method for reducing
spatter in a
pulsed arc-welding process. The method includes detecting a short during a
pulse period of a
pulsed arc-welding process using a controller of a welding system. The method
further includes
increasing a resistance of a welding circuit path of the welding system for a
first period of time to
reduce a welding current through the welding circuit path in response to
detecting the short. The
method also includes decreasing the resistance of the welding circuit path of
the welding System
for a second period of time immediately after the first period of time to
increase the welding
current through the welding circuit path. The method further includes
increasing the resistance
of the welding circuit path of the welding system for a third period of time
immediately after the
second period of time to reduce the welding current through the welding
circuit path in an-
ticipation of clearing the short. Increasing the resistance may include
opening an electrical
switch of a switching module disposed in the welding circuit path. Decreasing
the resistance
may include closing an electrical switch of a switching module disposed in the
welding circuit
path. The method may further include detecting that a short has cleared, and
decreasing the
resistance of the welding circuit path of the welding system in response to
detecting that the short
has cleared.
[0049] An embodiment of the present invention comprises a method for reducing
spatter in a
pulsed arc-welding process. The method includes detecting a short between a
workpiece and an
advancing wire electrode during a pulse period of a pulsed arc-welding process
using a Controller
of a welding system. The method further includes decreasing a current of a
welding circuit path
of the welding system for at least a portion of a determined period of time in
response to
detecting the short wherein, during most pulse periods of the pulsed arc-
welding process, the
determined period of time is of a duration allowing for the short to clear
without having to first
increase the current of the welding circuit path. Decreasing the current may
include increasing a
resistance of the welding circuit path. Increasing the resistance may include
opening an
electrical switch of a switching module disposed in the welding circuit path,
wherein the
switching module includes the electrical switch in parallel with a resistance
path. The method
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may further include increasing the current of the welding circuit path of the
welding System im-
mediately after the determined period of time if the short has not cleared.
Increasing the cur-
rent may include decreasing a resistance of the welding circuit path.
Decreasing the resis-
tance may include closing an electrical switch of a switching module disposed
in the welding
circuit path, wherein the switching module includes the electrical switch in
parallel with a resis-
tance path. The method may further include slowing down a speed of the
advancing wire elec-
trode in response to detecting the short between the electrode and the
workpiece. Slowing down
the speed of the advancing wire electrode may include switching off a motor of
a wire feeder
advancing the wire electrode and applying a brake to the motor. The brake may
be a mechanical
brake or an electrical brake, in accordance with various embodiments.
[0050] While the claimed subject matter of the present application has been
described with
reference to certain embodiments, it will be understood by those skilled in
the art that various
changes may be made and equivalents may be substituted without departing from
the scope of
the claimed subject matter. In addition, many modifications may be made to
adapt a particular
Situation or material to the teachings of the claimed subject matter without
departing from its
scope. Therefore, it is intended that the claimed subject matter not be
limited to the particular
embodiment disclosed, but that the claimed subject matter will include all
embodiments falling
within the scope of the appended claims.
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Reference numbers
100 electric arc welding system 172 switching command signal
110 switching module 180 waveform generator
111 electrical switch 181 output waveform signal
112 resistive path 210 welding circuit inductance
120 power converter 400 method
121 welding output 410 step
122 welding output 420 step
123 inverter power source 430 step
124 freewheeling diode 440 step
130 wire feeder 450 step
140 current shunt 500 waveform
150 current feedback sensor 510 peak pulse
160 voltage feedback sensor 520 time
161 signal 530 time
162 signal 540 short interval
170 high-speed controller 610 ball of molten metal
171 command signals 620 tether
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630 spatter E welding electrode
700 current waveform W workpiece
710 peak pulse
720 time
730 time
740 short interval
800 method
810 step
820 step
830 step
840 step
850 step
900 current waveform
910 peak pulse
920 time
930 time
940 short interval
960 blanking interval
19
