[jkey383]

I am trying to understand my new bobcat 250. My lincoln 305, which crapped out on me, had a crisp or soft setting. The coarse and fine adjustments on the miller allow me to switch from the 40-130 setting for a 3/32 to 1/8th, and 60 -150 for 1/8th to 5/32. Now somewhere in here, the current becomes different. I have found after many difficult welds that the higher coarse setting with a fine setting of about 3 will give me the much better root bead characteristics. The lower coarse setting seems to shower the arc and does not seem to push the bead in. Why is this? Help me understand why the machine does what it is doing so I can understand why I am doing what I am doing. Is there a site I can go to that explains this for the welding goober?

[DylanWelds]

http://m.youtube.com/watch?v=fvZGxFs0bJQ

I saw this video a while ago and maybe it might help maybe not. I watched the whole thing but don't have a machine with adjustments like that so never got to try it out.

[Otto Nobedder]

My "gut reaction" is, to produce two current ranges from a single fairly simple generator, the two settings have different "Open-circuit voltage". This is going to give different arc characteristics.

The Bobcat 250, though a fine machine, is "entry level" for generator welders.

I suspect you could prove this with a voltmeter.

Steve S

[O-1Stroke]

Fieldres has a very knowledgeable YouTube video on this subject. I have done some testing on his theory and now use it daily. It basically is about amperage versus current. On your fine adjustment the lower the number the lower the voltage, which would be better for a 7018. The higher the number the higher the voltage, which would give you more dig, say for a 6010. If you want more amperage but less voltage go higher on your main control and less on your fine control. For example,with 7018 3/32 on my miller bobcat I run on the second main setting ( it's second nature so I forget the amperage range sorry) and only 3 to 4 on the fine setting. And for a 7018 1/8 I run on the third setting and 3 to 4 on the fine. You get the amperage you required for the weld with less voltage for a smooth 7018 arc. You could leave it on the second setting and run up the fine adjustment to run the 1/8 rod, but the voltage will increase giving you a more harsh arc probably more suited for a 6010. I use this method and it works well for me. I hope I put it correctly.


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[O-1Stroke]

Sorry Dylanwelds, I didn't notice that was the video I was talking about.


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