Greetings All,
I have a handheld spot welder, the type used for autobody sheet metal
among other things. I am converting it to a stationary spot welder and
one thing that would be nice is to be able to limit the current for
thinner material. The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input side to reduce
the current? The welding current is 4000 amps and the suggested weld
times are specified in pulses at a pulse rate of 60 Hz. For example
the suggested weld time for .010" mild steel is 4 pulses. This is an
awfully short time period and I would like to make it a little longer
so that the timing periods allow more tolerance.

I have a handheld spot welder, the type used for autobody sheet metal
among other things. I am converting it to a stationary spot welder and
one thing that would be nice is to be able to limit the current for
thinner material. The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input side to reduce
the current? The welding current is 4000 amps and the suggested weld
times are specified in pulses at a pulse rate of 60 Hz. For example
the suggested weld time for .010" mild steel is 4 pulses. This is an
awfully short time period and I would like to make it a little longer
so that the timing periods allow more tolerance.

On Thu, 08 Feb 2007 07:48:10 -0800, Eric R Snow wrote:

I have a handheld spot welder, the type used for autobody sheet metal
among other things. I am converting it to a stationary spot welder and
one thing that would be nice is to be able to limit the current for
thinner material. The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input side to reduce
the current? The welding current is 4000 amps and the suggested weld
times are specified in pulses at a pulse rate of 60 Hz. For example
the suggested weld time for .010" mild steel is 4 pulses. This is an
awfully short time period and I would like to make it a little longer
so that the timing periods allow more tolerance.

Tolerance of what? Why do you want to lengthen the time period? If four
pulses weld .010" mild steel, then why change it? You put your parts in
the jaws, clamp them down, and weld. Do you want to do .005" mild steel?
Then try two pulses.

Or do you just want to slow it down so you can watch the weld taking
place in slo-mo? ;-)

Good Luck!
Rich
Greetings Rich,

Greetings All,
I have a handheld spot welder, the type used for autobody sheet metal
among other things. I am converting it to a stationary spot welder and
one thing that would be nice is to be able to limit the current for
thinner material. The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input side to reduce
the current? The welding current is 4000 amps and the suggested weld
times are specified in pulses at a pulse rate of 60 Hz. For example
the suggested weld time for .010" mild steel is 4 pulses. This is an
awfully short time period and I would like to make it a little longer
so that the timing periods allow more tolerance.
Thanks,
Eric

On Thu, 08 Feb 2007 19:17:04 GMT, Rich Grise <rich@example.net> wrote:


On Thu, 08 Feb 2007 07:48:10 -0800, Eric R Snow wrote:


I have a handheld spot welder, the type used for autobody sheet metal
among other things. I am converting it to a stationary spot welder and
one thing that would be nice is to be able to limit the current for
thinner material. The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input side to reduce
the current? The welding current is 4000 amps and the suggested weld
times are specified in pulses at a pulse rate of 60 Hz. For example
the suggested weld time for .010" mild steel is 4 pulses. This is an
awfully short time period and I would like to make it a little longer
so that the timing periods allow more tolerance.

Tolerance of what? Why do you want to lengthen the time period? If four
pulses weld .010" mild steel, then why change it? You put your parts in
the jaws, clamp them down, and weld. Do you want to do .005" mild steel?
Then try two pulses.

Or do you just want to slow it down so you can watch the weld taking
place in slo-mo? ;-)

Good Luck!
Rich

Greetings Rich,
I want to slow it down because the timing relies on how fast I can
turn it on and off. I'm the timer. When doing .005" sheet I melt
through too often.
ERS
get your self a high current mercury relay to run the xformer and

Eric R Snow wrote:

On Thu, 08 Feb 2007 19:17:04 GMT, Rich Grise
rich@example.net> wrote:


On Thu, 08 Feb 2007 07:48:10 -0800, Eric R Snow wrote:


I have a handheld spot welder, the type used for autobody
sheet metal among other things. I am converting it to a
stationary spot welder and one thing that would be nice
is to be able to limit the current for thinner material.
The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input
side to reduce the current? The welding current is 4000
amps and the suggested weld times are specified in
pulses at a pulse rate of 60 Hz. For example the
suggested weld time for .010" mild steel is 4 pulses.
This is an awfully short time period and I would like to
make it a little longer so that the timing periods allow
more tolerance.

Tolerance of what? Why do you want to lengthen the time
period? If four pulses weld .010" mild steel, then why
change it? You put your parts in the jaws, clamp them
down, and weld. Do you want to do .005" mild steel? Then
try two pulses.

Or do you just want to slow it down so you can watch the
weld taking place in slo-mo? ;-)

Good Luck!
Rich

Greetings Rich,
I want to slow it down because the timing relies on how
fast I can turn it on and off. I'm the timer. When doing
.005" sheet I melt through too often.
ERS
get your self a high current mercury relay to run the
xformer and
get 2 adjustable delay on timers.
the first timer gets started with your clamp switch to
insure you have
full compression. The first timer when it times out and
comes on will then start the second timer. the Second timer
will use a NC (normally Close) contact which will operate
the main Mercury relay to turn on your welder xformer.
when this second timer times out, the contacts will then
open and wait for you to release the clamp to start the
next cycle..
We did this once our self's for a shop, with the use of
timers we removed
the arching that takes place when you're clamping and
releasing because you never know when the switch gets out
of alignment with the electrodes and energize under light
contact.
Get your self short delay timers.

Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net
wrote in news:NYPyh.366$Hc5.159@newsfe05.lga:


Eric R Snow wrote:


On Thu, 08 Feb 2007 19:17:04 GMT, Rich Grise
rich@example.net> wrote:



On Thu, 08 Feb 2007 07:48:10 -0800, Eric R Snow wrote:



I have a handheld spot welder, the type used for autobody
sheet metal among other things. I am converting it to a
stationary spot welder and one thing that would be nice
is to be able to limit the current for thinner material.
The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input
side to reduce the current? The welding current is 4000
amps and the suggested weld times are specified in
pulses at a pulse rate of 60 Hz. For example the
suggested weld time for .010" mild steel is 4 pulses.
This is an awfully short time period and I would like to
make it a little longer so that the timing periods allow
more tolerance.

Tolerance of what? Why do you want to lengthen the time
period? If four pulses weld .010" mild steel, then why
change it? You put your parts in the jaws, clamp them
down, and weld. Do you want to do .005" mild steel? Then
try two pulses.

Or do you just want to slow it down so you can watch the
weld taking place in slo-mo? ;-)

Good Luck!
Rich

Greetings Rich,
I want to slow it down because the timing relies on how
fast I can turn it on and off. I'm the timer. When doing
.005" sheet I melt through too often.
ERS

get your self a high current mercury relay to run the
xformer and
get 2 adjustable delay on timers.
the first timer gets started with your clamp switch to
insure you have
full compression. The first timer when it times out and
comes on will then start the second timer. the Second timer
will use a NC (normally Close) contact which will operate
the main Mercury relay to turn on your welder xformer.
when this second timer times out, the contacts will then
open and wait for you to release the clamp to start the
next cycle..
We did this once our self's for a shop, with the use of
timers we removed
the arching that takes place when you're clamping and
releasing because you never know when the switch gets out
of alignment with the electrodes and energize under light
contact.
Get your self short delay timers.




The problem with electromechanical relays are the delays on
make and break. In the case of the spot welder, "make" delay
is no problem. But these delays are on the order of hundreds
of milliseconds. Since one cycle is ~16 mSec, once the timer
shuts-off the relay current, it would still power the welder
primary for 16 or more cycles. What he needs is an
electronic timer that can have a start-stop response time of
1 cycle @60Hz, and a solid state relay that can also respond
in that short of time. The SSR should have a current rating
twice that of the spot welder.

I built one of these several years ago, after trying to spot
weld 0.010" stainless with a large Miller LMSW-52
(220vac/2.5KVA) spot welder, without a timer. And the timer
that Miller sold cost more than the spot welder, and stand
w/foot operated tongs, put together. And it was
electromechanical, and was never ment to do really short
cycle times.

The one I put together is archived in the Metalworking
Dropbox 2001, under "Miller Time"

If I were doing a lot of light weight sheetmetal I would get
a lower powered spot welder.

Ken
yeah, that's all well and fine how ever, you must pay close attention

yeah, that's all well and fine how ever, you must pay close attention
to the type of SSR you use to insure zero crossing control ....

Phil Allison wrote:
"Jamie"

yeah, that's all well and fine how ever, you must pay close attention
to the type of SSR you use to insure zero crossing control ....


** Risky idea - ensures maximum possible " inrush surge " peak
currents every time.

Yep. A shorted secondary, current limited transformer (I think that is a
pretty good description of a spot welder) is mostly inductor. If you
could add logic to fire the SSR, on the first half cycle, near peak
voltage, the transformer would get less hot and so would the SSR. But the
shorted secondary also reduces the tendency of the core to saturate
(except for the small magnetic shunt), so it may not be so important.

"Jamie"


yeah, that's all well and fine how ever, you must pay close attention
to the type of SSR you use to insure zero crossing control ....


** Risky idea - ensures maximum possible " inrush surge " peak currents
every time.

Phil Allison wrote:

"Jamie"


yeah, that's all well and fine how ever, you must pay close attention
to the type of SSR you use to insure zero crossing control ....



** Risky idea - ensures maximum possible " inrush surge " peak
currents every time.


Yep. A shorted secondary, current limited transformer (I think that is
a pretty good description of a spot welder) is mostly inductor. If you
could add logic to fire the SSR, on the first half cycle, near peak
voltage, the transformer would get less hot and so would the SSR. But
the shorted secondary also reduces the tendency of the core to saturate
(except for the small magnetic shunt), so it may not be so important.
The problem i originally was stating is that Welders arc at various times.

"John Popelish"
Phil Allison wrote:
"Jamie"

yeah, that's all well and fine how ever, you must pay
close attention to the type of SSR you use to insure
zero crossing control ....


** Risky idea - ensures maximum possible " inrush surge
" peak currents every time.

Yep. A shorted secondary, current limited transformer (I
think that is a pretty good description of a spot welder)
is mostly inductor. If you could add logic to fire the
SSR, on the first half cycle, near peak voltage, the
transformer would get less hot and so would the SSR. But
the shorted secondary also reduces the tendency of the
core to saturate (except for the small magnetic shunt), so
it may not be so important.



** Wrong to assume the secondary is always effectively
shorted.

There will be very many occasions when the secondary is
open.

Expect inrush surge peaks equal to the AC voltage peak /
primary ohms.

My well exceed the SSR's repetitive I peak rating.

Splat.


........ Phil

** Wrong to assume the secondary is always effectively
shorted.

There will be very many occasions when the secondary is
open.

Expect inrush surge peaks equal to the AC voltage peak /
primary ohms.

My well exceed the SSR's repetitive I peak rating.

Splat.


In mine, I use the switch that is built into the lever
mechanism for the jaws. In the original design it was just a
power switch in the primary. Jaws close=power on...jaws
open=power off. But the switch operates after the jaws make
contact and before contact is lost. In my design it just
triggers my timer. No timing or primary current unless the
jaws are closed...and I don't open the jaws until the timer
has cycled off. I suppose this where you could get powered
open secondary...if you let up on the jaws on a long time
cycle.

Greetings All,
I have a handheld spot welder, the type used for autobody sheet metal
among other things. I am converting it to a stationary spot welder and
one thing that would be nice is to be able to limit the current for
thinner material. The input voltage is 220 volts @ 15 amps. Can I just
use an appropriately rated power resistor on the input side to reduce
the current? The welding current is 4000 amps and the suggested weld
times are specified in pulses at a pulse rate of 60 Hz. For example
the suggested weld time for .010" mild steel is 4 pulses. This is an
awfully short time period and I would like to make it a little longer
so that the timing periods allow more tolerance.
Thanks,
Eric