Mig equipment problem or user error?

By Oilburner Date 07-09-2003 10:23

I consider myself a beginner even after owning a Miller 135 for a couple of years now. My typical projects are shelves and tables made out of light gauge tubing. This past weekend, I was fabricating a reloading bench out of 1 1/2" 16 ga square tubing and ran into a problem.

After running many beads successfully, I noticed that I burned through a joint. When I tried to continue, I noticed that the wire developed a large orange globule at the end rather than laying down a good bead. This struck me as being very odd because I never have the time to see the wire melting, it's been, squeeze the trigger and weld. The machine seemed to sound a little different too. I did not change settings and previously, the sound was best described as "frying bacon". I checked to make sure I had gas, moved the ground closer to the point of work but have know idea what happened.

I am using .030 wire, a .035 tip and a C02/Ar mix.

The garage was very hot, possibly as high a 110 F with 95% humidity and the machine was on for about an hour and half if that makes any difference.

What could be the problem?

Thanks, Oilburner

By TimGary (****)

Date 07-09-2003 11:48

It's hard to say for sure from here, but it sounds like something is slowing down your wire feed. Check the contact tip first to be sure it's not dirty enough to slow down the wire.
If you have not adjusted the settings on the machine, and the tip is good, then it's probably time to clean out your gun and liner. The inside of the liner and gooseneck on the gun gets stopped up with dust and metal shavings after a while. A quick way to clean it is to remove it from the machine, remove the electrode wire, and blow out the liner with compressed air. Also, check the lead for damage. If something sharp and heavy enough to cut the insulation has fallen on the lead, it may have kinked the liner. That would require liner replacement.
Also, when you're welding, try to keep the gun and lead as straight as possible in order to reduce liner friction. If your lead is coiled around and under your feet, it won't feed properly.
You should check the drive rolls as well while your cleaning up the machine. Make sure they are tensioned properly and not worn out. If the wire groove in the rolls is worn out, it won't matter how much tension you apply, they still won't feed right.
While you've got the compressed air out, use it to blow the dust from the machine as well. Open up the casing enough to get the air nozzle inside and blow it out good. This will help it run cooler and prevent electrical shorts caused by metal dust.
Now that your machine is all cleaned up and maintenanced, try it again. If you still have troubles, come back and explain in a little more detail about what's going on.
Good Luck!
Tim

By CHGuilford (****)

Date 07-09-2003 16:31

I'm wondering if you didn't burn out a diode or something in your power supply. Usually if your wire binds or stops feeding, you burn back to the contact tip and ruin it. The arc gets longer but you still deposit metal at least for a moment . Since the wire just "balls up" at the end, it sounds like something changed your electrical characteristics.
Does your wire stop feeding, or does the wire form a ball at the end and stub off when it contacts the weld joint?

Chet Guilford

By jwright650 (*****)

Date 07-09-2003 17:50

Like Tim and Chet stated, it helps to blow out the machine to keep it cool and helps with keeping the electronics from overheating. Dust is a great insulator and will hold the heat in, which is bad for electronics. Blow off the spool with air too, this helps keep the liner and drive components from collecting dust. Most of the dust in shops have a combination of ingredients, but is mostly metallic particles from grinding, cutting and welding. All of which is bad for electronics too. I'm curious why you blew through the joint, I was wondering if something caused the current/voltage to rise and make you blow through, something like Chet stated about the elctronics. I know when a clothes dryer's heating element is about to burn out, it will get hotter than normal, just before it burns into. Again it's the amperage/voltage ratio off due to the resistance going *down* as the element starts to burn into and the element starts getting thinner in that spot. Keep us posted as to what you find out.
John Wright

By flashburner1 (*)

Date 07-09-2003 23:29

Hello,
Just curious - why are you using an .035 tip with .030 wire? A tip that is larger than your wire diameter allows berries/slag/crud to get in the tip and will cause the wire to drag. Try putting a new tip in - as posts above state it sounds like your wire is not feeding. Did your tip touch your work piece? Your machine has thermal overload protection - did it shut down when this happened?
Give more details as to what the machine is doing now when you try to use it.
Good luck,
Brian

By Oilburner Date 07-10-2003 01:39

Gentlemen, thanks for responding...

I checked the gun and cable and found no obvious signs of damage.

I checked the tip and I was incorrect, I am using a .030 tip. I believe one size larger was recommended for flux core wire and may have tried that at one time but in this case the correct tip was installed.

I check the wire tension which was set to the manufacturers specification which is 3 on the dial. One comment though, I cannot add any more tension and am not sure if this is a problem.

I checked the gas which was flowing 15 cfm (cfm?) and re-adjusted to 25 cfm per the manufacturers recommendation.

I checked the wire feed and watched the spool and tension rollers and did not see or feel any obvious signs of drag.

I ran several beads on butt jointed 1 1/2" tubing and could not duplicate the problem. I will clean the box, cable and gun this weekend. I don't have an air supply so I will have to use a portable air tank and it's late.

Thanks again for addressing my question, I'll search the archive for "newbie" posts :-)

By dee

Date 07-13-2003 02:55

John,
I agree with your comments and observations. I think a closer look at the characteristics of the break-down... the symptoms... is in order. We're doing a fair amount speculation, and I wonder if volt meter and a call to Miller wouldn't help abbreviate the process.

A parting comment on the comparison to a heating element though...your concept is accurate but I think you misspoke... the LESS resistance the hotter the element.

Regards,
d

By jwright650 (*****)

Date 07-14-2003 12:14

Hey there D!
Haven't see much from you on here lately, must be a busy man these days.Yep, I was typing away again without reading it back over. You're right it should read less resistance. Keep me in line:)
John Wright