Tig -> Mig? Dumb idea or....

Do this:

Update your will. Make sure your life insurance is paid up. Make sure your homeowner's policy will cover it. Get your firefighting equipment out, serviced, and ready. Get the kids and dog to a place of safety. Wear protective insulated PPE. Make your peace with God. Tell your family how much you love them.

Try it.

Alternative: go buy the equipment you need. It will cost less in the long run.

Less drama, but boring is okay.

Steve

James,

Some of the lower end MIG's are constantly hot as designed. I have used one of these and its really not an issue. Only suggestion I have is to verify the wire feed is worth a darn in the first place. I have used a bunch of lower end MIG's that the wire feed was so poor I spent more time fiddleing with the wire feed than welding.

With the 180 behind it you would have a nice variable amperage that you could match the wire feed speed to. You get really spoiled when you can set the wire feed speed and the amperage to get that perfect "frying bacon" sound and nice clean welds.

Skip the foot pedal idea. MIG's are more useful in the off-balance postions you just can't manage with a TIG.

Bart

"Bart D. Hull" wrote: (clip) With the 180 behind it you would have a nice variable amperage that you could match the wire feed speed to. ^^^^^^^^^^^^^^ Seems to me that I remember reading here, more than once, that MIG requires constant voltage, not the constant current that the stick welder supplies. Am I remembering it right?

No. The voltage / current characteristics of a stick or TIG welder are different from those of a MIG. This allows you to control the power of a stick arc byvarying its length, but makes the MIG arc self-controlling.

Besides which, rubbish MIG welders are dirt cheap. Only the good ones are still expensive, and even they aren't too bad (in comparison to TIG)

Just add a Readywelder spoolgun to the Miller 180 and dump the cheap MIG on eBay.

James,

As others have already indicated, there are several possible problems with this idea ... but since you ask, you might be the sort of person who will want to do it anyway. Even though it might be better / cheaper in the long run to buy a Ready Welder, you might be one of those folks that just like the challenge of scrounging up something from parts on hand. :) (I wouldn't know anyone like that, of course!)

The most significant issue you would have to deal with is that the 180SD is a constant current machine rather than the constant voltage that is needed for MIG. With constant current (stick/TIG), the voltage in the arc will change as you move the electrode closer or farther from the work, but the current will remain (relatively) constant. By contrast, with constant voltage (MIG), the voltage in the arc remains relatively constant when you move further or closer, but the current changes. This characteristic makes the wire feed process self-correcting: if the wire burns too far back, the wider gap results in a lower current, which slows down the burn rate. If the wire begins to stick out too far, the smaller gap results in a higher current, which increases the burn rate. The net effect is that the process self-corrects to maintain a fairly constant gap. If you run a wire feeder on a constant current source, you lose this automatic self-correction. As I understand it, the Ready Welder can work with a constant current power source because it is designed with feedback circuitry that senses the changing voltage in the arc and instantaneously changes the feed rate to compensate. I don't have any idea how difficult it would be to design such a feedback circuit ...

As second issue you would have to deal with, as others have pointed out, would be the quality of drive components. However, I have seen various descriptions on the internet where persons have made their own drive system for a homemade MIG machine, or a homemade spool gun. Unfortunately, I do not have those website addresses ... however, a google search on "welder wire feed homemade" turns up some interesting looking links.

Without a doubt the most economical approach is to buy a commercial unit--if you are calculating the economics in terms of professional welding, or in terms of the welding as a means to an end. But as I've pointed out in this NG before, if welding is a hobby, then time spent welding is the point, not necessarily getting a job done as quickly as possible. (Note that for many folks, *welding* may not be the hobby, or it may only be a lesser component of the hobby; making such-and-such by way of welding may be the hobby, so that the economics are measured in terms of how quickly or well such-and-such gets made.) If messing around with machines and electronics is a hobby for you, then building your own wire feed unit may be an end in itself.

Let us know if you decide to build something ... and how it turns out!

Andy

Hi Andy,

You mean, a guy that might build things like

This: (Induction Heater)

This: (Glass Milling machine) This: (Telescope mirror polishing machine) This: (Optical coating chamber) This (Big pair of binoculars) Or Gawd forbid this: (400cid death machine)

I have definitely decided to try and build the spool feeder, mostly because it sounds like a good challenge.

The question now is, do I try and fabricate a fancy digital PIC based speed controller, or just kludge some simple analog controller...

Thanks for the ideas gentlemen, its good to know the problems that need to be solved!

Take Care, James Lerch

(My telescope construction, Testing, and Coating site)

Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. Calvin Coolidge

Hi Andy,

Yeah-THAT type of guy :)