Mig Welder Problem-Need advice

   / Mig Welder Problem-Need advice #1  

TO_Bud

Silver Member
Joined
Feb 10, 2004
Messages
202
Location
St. Clair, Michigan
Tractor
2000 TC40D, TnT, 758B BH
Having a problem with my Millermatic Challenger 172 welder, hope the collective can point me in the right direction. I'm not a novice welder but I'm also not a pro but I've done a lot of welding with this welder over the last few years. I'm building a "Tree Scoop" bucket and was well on my way to finishing when I ran out of wire. Went and bought a new 12 # spool of ER70s and began welding again. All was well for about 20 minutes but then I started experiencing a lot of spatter and poor penetration of the weld. I'm using recycled 5/16 plate for the project and it has been a challenge to get it good and clean but it has been ground. Shielding gas is argon/CO2 mix and is the same tank. Not sure of the actual amperage I'm set at but per my chart I'm at my highest output. Speeding or slowing the wire feed is not helping. I took the cover off the welder and checked all my electrical connections-all good. Blew out any dust inside and blew out the hose to the handle. Reinstalled the cover and checked the volume of gas flowing with the trigger pulled. It does sound like maybe the whoosh is not quite as loud as it used to be but there is gas moving. I turned the regulator way up (50#) and the weld improved a little bit. That's it, any advice as to what to do is appreciated.

Thanks, Bud
 
   / Mig Welder Problem-Need advice #2  
You need to turn that gas back down to around 20-CFH!

I'd check your ground, make sure the cable is inserted properly into the clamp, and tight. Make sure the clamp is free of any corrosion.
 
   / Mig Welder Problem-Need advice
  • Thread Starter
#3  
Thanks Shield Arc. I have checked the grounding cable and clamp already and it looks good there. I run my gas about 25 most of the time I only turned it up to see if the weld would improve and it did somewhat but still not satisfactory. I've got it back down now, I'll turn it lower if that is where it should be. The manual talks of cleaning and/or replacing the wire liner. What symptoms present when the liner is a problem?
 
   / Mig Welder Problem-Need advice #4  
I run 18 to 20 CFH on my gas when Mig welding with all the doors closed in my shop, and 15 CFH for Tig welding, but I have a gas lens on my Tig torch.

Before I'd replace the liner, take the gun off the machine, remove the contact tip. Remove your oxygen gauge from your oxygen bottle. Place the end of your Mig gun that goes into the machine against the opening on your oxygen bottle, and crack the valve. That kind of air pressure should blow any crap out of the liner.;)
 
   / Mig Welder Problem-Need advice
  • Thread Starter
#5  
OK, I'll give that a try, thanks.
 
   / Mig Welder Problem-Need advice #6  
I run 18 to 20 CFH on my gas when Mig welding with all the doors closed in my shop, and 15 CFH for Tig welding, but I have a gas lens on my Tig torch.

Before I'd replace the liner, take the gun off the machine, remove the contact tip. Remove your oxygen gauge from your oxygen bottle. Place the end of your Mig gun that goes into the machine against the opening on your oxygen bottle, and crack the valve. That kind of air pressure should blow any crap out of the liner.;)

Also check the gas defuser in the gun. Are you using the same brand of er70s-6? Bad wire?
Other than spatter, how is the weld bead?

Heat = arc heat.
wire speed = amps.
 
   / Mig Welder Problem-Need advice #7  
Could be you're losing your shield gas.
Close the valve on the bottle and see if the high pressure gauge drops, if it does you've got a leak between the bottle and the gas solenoid in the machine. If it doesn't drop, try this:
If you have a ball type flowmeter: Open the valve, loosen the feed rolls and hold your hand over the nozzle and pull the trigger. The flowmmeter will rise a bit due to the gas going back thru the liner but it shouldn't go up to the full flow. If it goes up you've got a leak from the solenoid to the nozzle, could be a loose fitting, busted hose in the lead if you've dropped something on it for instance.
If you have a regular gauge type flow meter it's a bit harder as the needle stays set. You basically have to do the same thing but watch the gauge for a movement.
How tight is the friction on the wire spool, you just want it tight enough so it doesn't freewheel when you release the trigger.
No spatter on your contact tube, even a bit will cause the arc to go all wonky.
When the liner goes bad it usually causes burn back (the wire will 'burnback' t the contact tube). Sometimes you can feel the slight vibration when the wire sticks in the liner.
Have a look at the guide tube that aligns the wire to the liner right after the drive rolls. If you don't use wiper pads on your wire the wire coating will eventually cause the hole to tighten up and cause feed problems.....Mike
 
   / Mig Welder Problem-Need advice
  • Thread Starter
#8  
Transit - Had my gun apart and it is a simple device with a spring loaded trigger with electrical contacts on it. Depress the trigger and the contacts energize the gas solenoid which routes gas up the hose at the hose base. Seems to be working OK in that respect. Using the same type of wire ER70-s but a different brand, however the welder was working well for 15 - 20 minutes on the new spool. The bead is not penetrating the work stock, it is mounding on the stock not biting in. I was able to finish the job by turning up the shielding gas rate by double for the last half hour. Welds were still not what they should be but should suffice for what it is.

mrmickey - I just went out and checked my regulator gauges, the high side (psi) was showing 500# and the cfh gauge was at 40. I did shut the tank off about 5 hours ago so keep that in mind. When I opened the tank valve just now the psi went to 1000# and the cfh gauge stayed at 40. I have it set for 25 while welding. I don't have the ball type flowmeter, just the regulator. The cfh gauge does drop 5 while operating the gun if I understand you correctly. I have backed off the spool friction to just stop feewheeling, barely any friction. The wire feeds continuously when the trigger is pulled and not welding. You may be onto something regarding the liner, there is a definite pulsing feeling while welding that is not there when I pull the trigger while watching the wire feed rate away from the work stock (not welding). I'll check out the guide tube in the morning to see if there is any buildup.

Thanks guys.
 
   / Mig Welder Problem-Need advice
  • Thread Starter
#9  
Follow-up post. Followed all suggestions above and did some more on my own. I pulled the hose tube from the drive assembly and pulled out the liner. There was some debris on the liner here and there. Blew out the tube like Shield Arc suggested. Checked the defuser in the gun and it was good. The liner looked good, at least no apparent burn marks on the outside. When I reassembled the tube into the drive assembly I found I could push it in farther than it was when I disassembled. It appears the 1st O-ring may not have been totally past the shielding gas inlet inside the drive assembly. Put everything back together, set the regulator to 20 CFH, and laid down a nice pretty bead. Thanks for all the help.
 
   / Mig Welder Problem-Need advice #10  
Just logged on and started reading this thread. I was all set to tell you to clean the gun, liner and hose but decided to read on first.

Glad to see you got it fixed.
Now you need to make cleaning both the gas hose and the wire liner a regular chore. I took an old air blow gun, attached an air needle (used to blow up footballs or basketballs) and cut the end off the needle.

It fits in the hose and/or the liner easily and with my air compressor set at 100 Lbs plus, it cleans it out very quickly.

We blow out all the machines, hoses and torches every Friday in my shop. I can't afford to have downtime and it's a quick, easy maintenance step.
 

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