MIG

Date 02-01-2007 20:24

Hey All

Dont mean to lower the conversation here but I need some help with MIG welding. I have only worked with a basic Miller with a voltage dial and a wire feed dial--adjust until you have correct penetration and no splatter. (Not that I was ever good at tuning one of those either)
This new machine is giving me alot of grief and if I could pick the darn thing up, I would toss it out the window.
It is an AFTEK MV 445, hooked to a Thermal Arc 2410 (the wirefeed/gun component). The gas is 75AR/25CO2. The tech came at one point and the machine is in good working order--so I cant blame it on that. The demand pulse knob is turned up all the way--where the tech had it--but I might have switched the gas since he's been here. I am pulling the gun (should I be pushing) and the voltage is set at 85 and the wire feed is 2.5 (the knob seems very sensitive, I just breathe on it and it makes a big difference). The material is 3/16" mostly butt joints, with a few fillet joints.
The problem isnt so much penetration, it is the look of the bead. I dont have any splatter, but either I have too much build up or it is pretty flat with a ridge in the center--both ugly to my eye. How do I get a bead that looks good?
Remember I am a TIG welder so I might be expecting something that isnt possible. Pictures would be a great help--all I have found (so far) are photos of people learning to weld on their old clunkers in Britain.

Rebekah

By Lawrence (*****)

Date 02-01-2007 20:36

If you have a week go to Weldreality.com and look for Ed Craig's "clock method" for setting GMAW parameters.

Lots of questions before you can get a solid answer. But here are some thoughts.

1 If you are trying for spray transfer even with pulse 75/25 is the wrong gas. 80% argon minimum is required.

Whether Spray or Short Circuit your arc voltage will be between about 17 and 30 volts... Maybe your machine and it's *85* is a percentage of total available voltage. Or your machine is a CC/CV and it is set in Stick/Tig mode and you are reading 85 open circuit volts... if this is the case. Switch to CV/Mig mode and the voltage should be more reasonable.

My advice is to turn the pulser off until you master short circuit and spray transfer modes and understand why things happen the way they do.

For short circuit transfer a drag angle produces best penetration. A push angle may be used for vert welds with uphill progression or on thin sheet metal to reduce burn through.

For Spray Transfer GMAW always run a push angle.

3/16 can be welded with either short circuit, spray or GMAW-P

By Lawrence (*****)

Date 02-01-2007 20:45

Here is exact data that will also serve. Hobart Bros. make the best data sheets I've seen for electrodes. They will give performance parameters for each electrode, each diameter and with most shield gas combinations. Follow these and you will be very close and need minimal tweaking.

ER70S-3
http://www.hobartbrothers.com/pdf/datasheets/HB_25.pdf

ER70S-6
http://www.hobartbrothers.com/pdf/datasheets/HB_28.pdf

By Logan Mayfield (**)

Date 02-01-2007 21:00

We run GMAW-P and our standard use to be drag only. I have since changed the standard to either a push or pull as long as there travel angle does not exceed 15 degrees. You stated that you should ALWAYS run a push angle with spray transfer, is this also the case for pulsed spray? What is the reasoning for a push only with spray? Most of the material I have read recommends a drag methode because you have better shielding of the molten puddle and get better penetration. However I have found that a satisfactory weld can be obtained with the push methode as well. You still get adequate penetration and shielding as long as you travel angle is not to great. What is you opinion here?

Rebekah, shielding gas selection will effect the amount of penetration and the finish contour of the weld. You might ask your gas supplier for a recommendation that will meet your needs.

By Lawrence (*****)

Date 02-01-2007 21:42

Logan,

Spray transfer GMAW is a high deposition, high speed wet pool mode compared to short circuit. A drag angle with Spray transfer leads to lack of fusion as it is not possible to to keep the wire consistantly at the leading edge of the weld pool. If the wire fades back into the pool the metal simply piles to make an overly convex profile with overlap or spreads too wide and produces lack of fusion at side walls. A 10 to 15 degree push travel angle should not have an ill effect on shield gas coverage. (this is what most training institutions, textbooks, manufacturers recommend)

Traditional Spray transfer GMAW (steel/stainless) is limited to the flat and horizontal fillet positions, It can be run vertical with downward progression, but this risks spatter and side wall fusion issues.

We have some local manufacturers that run Globular parameters vert-down to increase productivity. But I don't think it is the best way to achieve maximum soundness.

GMAW-P by it's nature has the benefits of Spray transfer with a more controllable weld pool. Still it is generally run with a push angle even in robotic applications. GMAW-P can be run Vert-up with proper parameters.

By Logan Mayfield (**)

Date 02-02-2007 01:45

I'm glad we got to chat. That is the first time I have heard of dragging not being the recommended travel methode.

I am well aware of the benefits of using the GMAW-P mode of transfer. Its pros are little to no spatter, less smoke, good in all position welding, and can be used on thick or thin material. The Limitations are that you need good fit up and also the cost of the complex equiptment.

By monsoon12 (**)

Date 02-01-2007 21:01

What size wire are you running?

By DaveBoyer (*****)

Date 02-02-2007 04:31

If You visit WeldReality.com You cant help noticing Ed's lack of enthusisiasm with ALLMOAST ALL of the pulsed power sources. Are they really that bad?