Wire Feed Welder Setting Question

I bought a new used Miller CP-302 power supply/S-74D wire feed combo. I have a question on setting wire feed/volts.

I also have a miller 252 which I have always just used the chart that it has for settngs and it works pretty well. No such thing is available for the CP-302/feeder combo. Looking on Millers site they give suggestions but they talk about wire feed/amperage settings. I see this same thing in several places where they talk about wire feed and amperage settings. Since mig welding is constant voltage and voltage is the setting. How does this work? I understand maybe some trial and error may be needed to get things set but still it seems like there ought to a rule to come up with a starting point.

I suppose I can use the chart from my 252 but I'd like to understand this a little better.

I use a Miller app you can find on the web. On my Android phone.

wow, to "understand this a little better" ....


ok, so you want a 2 year technical collage syllabus in a short post? not possible. there are literally hundreds of variables, and the reason the CP-302 doesn't come with a "chart" is it is assumed that professionals will be setting it up who have some clue what they are doing. id suggest you get back on the internet and start searching "GMAW transfer modes" "GMAW parameters for [whatever it is you are trying to do with said welder]".

sorry to be a bit harsh, but the "rule" is to put at least some effort to educating yourself BEFORE getting on a professional forum. asking a wildly open ended question without giving even a clue what you are trying to weld, and what with, other than the machine, just doesn't cut it around here.

happy to share knowledge, as are most on here, but ask a slightly informed question, and you will get plenty of replies.

Hey now ! ^^^
Pull trigger, brite lite, loud noise....how hard can it be ?

digger doug said:

Hey now ! ^^^
Pull trigger, brite lite, loud noise....how hard can it be ?

Click to expand...

haha! well that's how I learned

cyanidekid said:

haha! well that's how I learned

Click to expand...

Next semester.....Here's a helmet, let's see some improvement.....

cyanidekid said:

wow, to "understand this a little better" ....


ok, so you want a 2 year technical collage syllabus in a short post? not possible. there are literally hundreds of variables, and the reason the CP-302 doesn't come with a "chart" is it is assumed that professionals will be setting it up who have some clue what they are doing. id suggest you get back on the internet and start searching "GMAW transfer modes" "GMAW parameters for [whatever it is you are trying to do with said welder]".

sorry to be a bit harsh, but the "rule" is to put at least some effort to educating yourself BEFORE getting on a professional forum. asking a wildly open ended question without giving even a clue what you are trying to weld, and what with, other than the machine, just doesn't cut it around here.

happy to share knowledge, as are most on here, but ask a slightly informed question, and you will get plenty of replies.

Click to expand...

Well gee you could just have said you didn't know either with much less words. The Miller does have guidelines that I did search and find. Just not sure why they talk about amps as a variable that is controllable on a constant voltage power source.

And, regarding the app i have it too and it specifies wire feed and current.

I use "Pocket Welder Helper" App on my phone. Gives wire speed and voltage range along with expected amperage range. CP-302 doesnt have amp reading but my 350P displays Amps while welding which is a nice double check sometimes

Pete Deal said:

Well gee you could just have said you didn't know either with much less words. The Miller does have guidelines that I did search and find. Just not sure why they talk about amps as a variable that is controllable on a constant voltage power source.

And, regarding the app i have it too and it specifies wire feed and current.

Click to expand...

oh, so it wasn't welding parameters you were asking about, it was basic principles of electricity? how could I know what exactly you were asking, with that vague post? so, now look up "welding power supply output characteristics" if you do a little research, you will find out that all power supplies have some "droop" and although GMAW units are described as "constant voltage" that is only compared to a GTAW/SMAW "constant current" unit. the only parameter of "heat" is current, so if you want to quantify the nature of the arc, amps is the way to do that.. different units will produce a given amperage at different voltage settings. that help?

Pete Deal said:

Well gee you could just have said you didn't know either with much less words. The Miller does have guidelines that I did search and find. Just not sure why they talk about amps as a variable that is controllable on a constant voltage power source.

And, regarding the app i have it too and it specifies wire feed and current.

Click to expand...

I also have a Miller 252 and have often asked myself the same questions about settings. It's true that it's a little confusing since the 252 and other MIG/MAG machines are adjusted in voltage rather than amps.

That being the case, I've learned to use the Miller charts on the machine as a rough starting point. In my case, I dial those settings back a little since I weld with 100% CO2, which is somewhat hotter in nature. The settings on the charts are actually not too bad.

As to the Cyanide fellow, there are some folks who particularly enjoy kicking peoples' asses on this site when they ask for information. I've never understood this propensity. Perhaps it stems from some difficult personal issues leading to misplaced aggression.

As you mentioned, from his comments, I gather that he doesn't know either.

The attached photo shows the welding parameters for Hobart's Excel Arc wire. It shows wire feed speed, volts and the amperage you get using those settings.
Also note the contact tip to work distance as that has an effect as well. Find the data sheet for the wire you want to use and you are set.

Cyanidekid is right, there are waaaaay too many variables to cover on a forum post. That said, we can give you some tips to get started.

-Use the Miller app to get rough parameters based on gas, wire, material, desired amperage, and application.
-Learn what each parameter does (voltage, wire speed, gas flow, travel speed, stickout distance) and how to optimize your settings.
-Research the different transfer types (short circuit, globular, spray transfer) and where there should be used.
-Last but not least, practice!

Fabworks said:

The attached photo shows the welding parameters for Hobart's Excel Arc wire. It shows wire feed speed, volts and the amperage you get using those settings.
Also note the contact tip to work distance as that has an effect as well. Find the data sheet for the wire you want to use and you are set.

View attachment 308456

Click to expand...

Thanks that gives some starting info.

Part of the issue is that the machine is not useable yet. I got it from HGR and it's very nice for HGR but the guides are missing so I have them on order, also the weld leads need to be replaced so at this point I am just thinking about it.

From my archived welding wisdom postings:

1. Remember: the wire speed controls fill and the voltage controls spread. For
example, to get a larger weld size, increase the wire to get more fill and
increase the voltage to spread the extra weld metal evenly.

2. Both the wire speed and voltage can be adjusted independently from each other
to change the arc characteristics, if small adjustments are made. However, if
large setting changes are made, both wire and voltage must increase or decrease
together.

3. Once the overall heat level (meaning the combination of BOTH wire and
voltage) is set for the correct weld size, the machine settings should be tuned
so that the arc makes a sharp, crisp, crackling noise. If the arc is making a
popping sound and droplets of molten metal appear on the end of the wire,
increase the wire speed OR decrease the voltage until a crisp crackle is heard.

4. It is possible for the arc to have a crisp crackle sound, but to have too
much wire OR too little voltage. In the case, weld will appear cold and high-
crowned. It will have steep, high sides and will not wet or flow smoothly into
the base metal. If the welds are showing high crowns and lack of fusion at the
edges, EITHER increase the voltage OR decrease the wire.

5. Within the correct operating range, increasing the voltage OR decreasing the
wire will give a more fluid weld pool and better fusion. Within the correct
operating range, decreasing the voltage OR increasing the wire will cause the
weld pool to fill up and freeze faster, which is helpful in out of position
welding.

Someone above seems to think that Real Men Know How To Set MIG Welders. Hmm - I thought the issue of welding and Real Men was settled a long time ago:

Pete Deal said:

Thanks that gives some starting info.

Part of the issue is that the machine is not useable yet. I got it from HGR and it's very nice for HGR but the guides are missing so I have them on order, also the weld leads need to be replaced so at this point I am just thinking about it.

Click to expand...

speaking of weld leads, the gauge and length affect the voltage setting required to get the current desired at the weld,(ohm's law and all that), as do all connections, ground clamp, work resistance etc.etc.. so another reason weld current is specified instead of voltage. a current meter is really handy to fine tune settings.

Newman109 said:

I also have a Miller 252 and have often asked myself the same questions about settings. It's true that it's a little confusing since the 252 and other MIG/MAG machines are adjusted in voltage rather than amps.

Click to expand...

To be fair, they're really adjusted in both voltage and amps. The wire feed speed is actually amperage even though that isn't how it gets displayed.

I've seen a Miller chart that explained how they use a wire diameter multiplier and output amperage to come up with the wire feed IPM, but that was more theory than practical application. It probably wouldn't be hard to reverse the equation to get amperage from a known IPM, but I've never even thought about needing to do so.

I had a MM252 for quite some time and got a crazy deal on a 350P so I sold it, but always liked how it welded...really nice units.

G-ManBart said:

To be fair, they're really adjusted in both voltage and amps. The wire feed speed is actually amperage even though that isn't how it gets displayed.

I've seen a Miller chart that explained how they use a wire diameter multiplier and output amperage to come up with the wire feed IPM, but that was more theory than practical application. It probably wouldn't be hard to reverse the equation to get amperage from a known IPM, but I've never even thought about needing to do so.

I had a MM252 for quite some time and got a crazy deal on a 350P so I sold it, but always liked how it welded...really nice units.

Click to expand...

That's interesting. Thanks!

The 252 does an excellent job. I've welded half inch plate with it to build a stand for my Bead Roller. It's really quite a machine.

A friend has a Miller 200, the grandfather of the 252, that has been used constantly in his weld-machine shop for more than 30 years and it's still going strong.

What got me into this is that I bought a Pipe pro 304. This is a diesel engine driven inverter welder with a 12k generator. Seemed like a handy thing on many fronts. It's basically a XMT 304/generator combo. I started looking for a wire feeder for it and found this combo I asked about here for about the price I was seeing wire feeders alone (used) for. My only complaint with my 252 is that it it's not too convenient for bigger stuff but I agree the 252 is really a nice machine. I hope the separate wire feeder will allow a little more mobility.

Pete Deal said:

What got me into this is that I bought a Pipe pro 304. This is a diesel engine driven inverter welder with a 12k generator. Seemed like a handy thing on many fronts. It's basically a XMT 304/generator combo. I started looking for a wire feeder for it and found this combo I asked about here for about the price I was seeing wire feeders alone (used) for. My only complaint with my 252 is that it it's not too convenient for bigger stuff but I agree the 252 is really a nice machine. I hope the separate wire feeder will allow a little more mobility.

Click to expand...

Something like a Pipe Pro 304 is a real processional rig. That's out of my league. I used to do a lot of welding back when I was racing motorcycles. Now I'm pretty much a hobby welder, although I've been welding for many years.

The 252 is no longer built by Miller since they, like other companies have moved into inverters and multi-use machines. I do a lot of reading on the Internet and some of the horror stories about the PC boards are rather frightening! Prices start at $1K on up for replacements. Admittedly, they are generally quite reliable. but still.......

I found a few really good videos on the some MIG basics in a little more detail than I have seen before. I thought would be useful to post here as a follow up to this thread. The guy (Nathan Farquharson) has other videos that seem very good too.

As G-ManBart said this guy talks about wire feed rate as being corelated to current. Also he mentioned that starting settings are from the wire manufacturer, which I looked and found to be true.

Short Circuit:
gmaw sc - YouTube

Spray Transfer:
spray transfer - YouTube