[Mikeover]

I'm practicing sheet metal welds, 20ga. (.037) steel using a Lincoln 256 power mig, .023" wire, with correct tip, liner, feed rollers, straight CO2. Often the wire on arc initiation simply vaporizers back into the contact tip & sticks inside at least for a moment. Settings are 200 ipm @ 17.4 volts.

I've tried swapping tips, and various roll force settings - no appreciable changes.

What's happening, and how to cure?

Thanks!

[Homemade]

I’m no expert, but I’d try more wire feed speed.

[Mike Westbrook]

Does that Lincoln have a dial for run in if so try changing it if it's set low it will start slowly then come up to set ipm I have a Lincoln sp 255 and it has a very hot start but never vaporized the wire

[Poland308]

You may want to do the count to 6 as you feed wire trick. Just to confirm that it’s feeding at the speed your set for. Other thing to check is if your feed rollers aren’t too big.

[weldin mike 27]

Check the tension nut on the middle of the spool. If it's over tight, the wire can't feed and burns back. Too loose and the spool free wheels after stopping.

[Mikeover]

Thanks to all for the replies - I usually weld much thicker material so practicing on sheet metal with this issue has been frustrating.

After online searching someone had reported success with electrode negative - that Did Not Work for me - vaporized the wire every time, just in case someone else looks for a solution.

What did work - using the run in control to reduce initial wire feed speed which seems to me counter intuitive, and thoroughly cleaning seemingly clean metal.

The problem still occurs though with much reduced frequency - even tried a larger contact tip to no avail.

What I do puzzle over is - this is a constant voltage machine, yet if the setting is for 17.4 volts it has been observed to display at times almost 28 volts after arc initiation.

Doesn't seem correct to me. I am of the belief that the voltage should stay constant while the amperage should increase as needed. if this is not correct, please let me know...

Thanks!

[cj737]

What did work - using the run in control to reduce initial wire feed speed which seems to me counter intuitive, and thoroughly cleaning seemingly clean metal.

The problem still occurs though with much reduced frequency - even tried a larger contact tip to no avail.

What I do puzzle over is - this is a constant voltage machine, yet if the setting is for 17.4 volts it has been observed to display at times almost 28 volts after arc initiation.

Doesn't seem correct to me. I am of the belief that the voltage should stay constant while the amperage should increase as needed. if this is not correct, please let me know...

Thanks!

From your description above, it sounds as though you might be long-arcing too?
I think you might find this helpful and informative. https://www.lincolnelectric.com/en-gb/s ... utput.aspx

[Poland308]

The voltage spikes are common as the droplets form and travel from the wire to the puddle. Short circuit transfer operation normal.

[Mikeover]

Ah, cj737 - thanks for the link. From the explanation:

To do this, the welding output needs to maintain voltage at a constant level (i.e., CV), so that the resulting arc length is consistent. Current is a less controlling variable. It is proportional to, or a result of, the WFS. As WFS increases, so does current and vice versa. With CV output, voltage and WFS are your preset, controlling variables and current is simply measured while welding.

That explains then why the reduced run in WFS also reduced the wire vaporization events.

But, from the CV chart voltage should vary a small amount; I consider jumping from 17.4 to 28 volts a very large differential.

I've tried holding the gun at a fixed distance from the workpiece while observing the voltmeter - it also displays a very wide variation from setpoint, so I'm thinking that my technique is not at fault (of course!).

Trying not to geekout on this but I may set up an oscilloscope to view current vs voltage while welding.

Thanks!

[starvncoyote]

When my machine starts feeding funky, I start checking the consumables. The wire feed guide and the liner are last on the mind and can do the most frustrating things.