After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let it
cook a while, but it was a perfect weld, as far as I can tell (peel
test). I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Bob

Oh - and nothing in the setup was particularly warm after the test.
Nothing to hot to touch.

Bob

Bob Engelhardt writes:

After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let
it cook a while, but it was a perfect weld, as far as I can tell (peel
test). I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Neat! I'd be curious to see the plans.

"Bob Engelhardt" wrote in message
. ..
After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let it
cook a while, but it was a perfect weld, as far as I can tell (peel test).
I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Bob

Holy Hannah!
What a beauty!

Did the lights in your house go dim during the weld?

--
Jeff R.

"Joe Pfeiffer" wrote:
Bob Engelhardt writes:

After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let
it cook a while, but it was a perfect weld, as far as I can tell (peel
test). I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Neat! I'd be curious to see the plans.

Myself as well; I have about fifty MOTs (for HV work), and would be curious
to see the schematic.

Jon

Haven't seen your design, but my .02 anyway-if you are switching the
primary with a SS relay, be careful of letting it cook as you described.
The first indication the relay is overloading is when it pukes. How
about posting some pics and a schematic in the dropbox?
Mine:
http://www.metalworking.com/dropbox/...retired_files/
See welder00.txt and the associated jpgs
JR
Dweller in the cellar

Bob Engelhardt wrote:
After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let it
cook a while, but it was a perfect weld, as far as I can tell (peel
test). I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Bob


--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth
If you're not the lead dog, the view never changes
Doubt yourself, and the real world will eat you alive
The world doesn't revolve around you, it revolves around me
No skeletons in the closet; just decomposing corpses
--------------------------------------------------------------
Dependence is Vulnerability:
--------------------------------------------------------------
"Open the Pod Bay Doors please, Hal"
"I'm sorry, Dave, I'm afraid I can't do that.."

On Sat, 1 Sep 2007 10:38:45 +1000, "Jeff R."
wrote:

"Bob Engelhardt" wrote in message
...
After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let it
cook a while, but it was a perfect weld, as far as I can tell (peel test).
I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Bob

Holy Hannah!
What a beauty!


Indeed! Very impressive!

Schematics!!

Encore!!

Gunner

Jeff R. wrote:

"Bob Engelhardt" wrote in message
...

After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let it
cook a while, but it was a perfect weld, as far as I can tell (peel test).
I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Bob


Holy Hannah!
What a beauty!

Did the lights in your house go dim during the weld?

Never had a problem with the lights with either of my spot welders the
larger being 2kVa but I run them of a 230V 30A supply. I've learned not
to wear my analogue electronic watch at the same time though as it
causes it to alter its time quite dramatically, never done any permament
damage as far as I can tell though.


--
Jeff R.

The weld looks like a beautiful 20 year old girl, but I would also be
interested in seeing the machine that did it!

i

Joe Pfeiffer wrote:
Neat! I'd be curious to see the plans.

Well, there aren't any plans (Plans! We don't need no steenkin'
plans!). It's just something that I made up. I will be posting to the
DropBox, once it's gotten stable - my "designs" tend to need a little
tweaking after I've used it a bit.

Bob

Jon Danniken wrote:
... and would be curious to see the schematic.

It's easy enough to describe with words: 2 microwave oven transformers;
their primaries in series, connected to 240v. The secondaries replaced
with 2 turns of the heaviest wire that will fit & connected in parallel.

That's it.

Bob

Jeff R. wrote:
Holy Hannah!
What a beauty!

Did the lights in your house go dim during the weld?

Thank you! No, it's was connected to a 240v, 50a welder circuit. But
it only draws about 16a.

Bob

Bob Engelhardt wrote:

After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let it
cook a while, but it was a perfect weld, as far as I can tell (peel
test). I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Bob


Excellent, the first time I read it I didn't pick up on the 1/8" part. Well
done! The stuff we spot weld at work isn't nearly that thick.

No wonder that others asked about your lights dimming. Tell us more.

Wes

JR North wrote:
Haven't seen your design, but my .02 anyway-if you are switching the
primary with a SS relay, be careful of letting it cook as you described.
The first indication the relay is overloading is when it pukes.

An SSR may be in its future, but now I was just closing a contactor.
About the cooking though - if I was well below the current rating of the
SSR, would it be OK? Say drawing 16A on a rated 25A SSR?

Also about the SSR: I've read that they should be derated 30-70% for
inductive loads. They were probably referring to motor loads, but the
spot welder is certainly inductive. As much as a motor, though? Did
you derate yours?

How
about posting some pics and a schematic in the dropbox?
Mine:
http://www.metalworking.com/dropbox/...retired_files/
See welder00.txt and the associated jpgs

I knew there was one in the DropBox! I'll be posting mine, as soon as I
use it some and work the kinks out. There are always kinks! Meanwhile,
here's a pic in it's prototype stage:
http://home.comcast.net/~bobengelhardt/welder.jpg

Bob

Bob Engelhardt wrote:
Also about the SSR: I've read that they should be derated 30-70% for
inductive loads. They were probably referring to motor loads, but the
spot welder is certainly inductive. As much as a motor, though? Did
you derate yours?
Bob

A transformer with a resistive load, which the weld is,is not very
inductive. Mostly only leakage inductance. So there shouldn't be
much of a spike regardless of what part of the cycle it isinterrupted on.
...lew...

Bob Engelhardt writes:

Joe Pfeiffer wrote:
Neat! I'd be curious to see the plans.

Well, there aren't any plans (Plans! We don't need no steenkin'
plans!). It's just something that I made up. I will be posting to
the DropBox, once it's gotten stable - my "designs" tend to need a
little tweaking after I've used it a bit.

Saw the picture, saw the schematic for the other one in the dropbox
metalworking.com (what a great resource! I hope that at some point
Practical Micro Design does put some advertising up -- they deserve to
get something back for their contribution).

Now, that doesn't look so bad...

Lew Hartswick wrote:
A transformer with a resistive load, which the weld is,is not very
inductive. Mostly only leakage inductance. So there shouldn't be
much of a spike regardless of what part of the cycle it isinterrupted on.
...lew...

That's right, it's the secondary load that matters. We used to refer to
it being "reflected" back as the primary load, factored by the turns ratio.

Thank you, that makes my using a 25A SSR reasonable.

Bob

"Bob Engelhardt" wrote:
Jon Danniken wrote:
... and would be curious to see the schematic.

It's easy enough to describe with words: 2 microwave oven transformers;
their primaries in series, connected to 240v. The secondaries replaced
with 2 turns of the heaviest wire that will fit & connected in parallel.

That's it.

Interesting; thanks, Bob. Any of the MOTs I have "played" with saturate
above 90VAC with the secondaries shorted; how much input current are you
seeing on this thing?

Jon

Bob Engelhardt wrote:
JR North wrote:

Haven't seen your design, but my .02 anyway-if you are switching the
primary with a SS relay, be careful of letting it cook as you
described. The first indication the relay is overloading is when it
pukes.


An SSR may be in its future, but now I was just closing a contactor.
About the cooking though - if I was well below the current rating of the
SSR, would it be OK? Say drawing 16A on a rated 25A SSR?

Also about the SSR: I've read that they should be derated 30-70% for
inductive loads. They were probably referring to motor loads, but the
spot welder is certainly inductive. As much as a motor, though? Did
you derate yours?
Right. I have one on my air compressor, and I am now using a 50
A, 400 V SSR on a motor that draws 11 A nominal. But, it has to
start the motor. It was running the motor almost continuously
all day today, with lots of starts, and no trouble (it has done
the same service before, too.) But, I did have problems with a
25 A SSR on that motor - well, just one problem, it shorted out.
The welder may not have the same sort of starting surge as a
motor, though, so the current derating may not be such a
problem. 16 A at 230 V is about 3700 W, that should be able to
melt a tiny button of metal.

Jon

Bob Engelhardt wrote:
After trying a couple of piece=of-cake welds, I thought I'd push the
envelope and tried it on 2 pieces of 1/8" mild steel. It had to let it
cook a while, but it was a perfect weld, as far as I can tell (peel
test). I don't think that I need to try for anything thicker 8-)

http://home.comcast.net/~bobengelhardt/weld.jpg

Bob

As another poster states, 1/8" is a pretty mighty spotweld, you're doing
very well with it.

I've got a bit ol' Miller AC welder I've been keeping for making a
spotwelder from, maybe your results will inspire me.

Whatcha usin' for tongs there?

John

JohnM wrote:
...
Whatcha usin' for tongs there?

Aluminum bars with copper tips.

Jon Danniken wrote:
... Any of the MOTs I have "played" with saturate
above 90VAC with the secondaries shorted;

I suppose that one needs a 'scope to see saturation? At any rate,
saturated or not, it works and I'm not going to worry about keeping it
out of saturation, unless it was a trivial fix.

how much input current are you seeing on this thing?

One measurement I took started at 13A & climbed to 16 as it cooked.

Bob