Pulse Spray MIG Overhead
We recently had a viewer ask "My question is does that stick out you mentioned apply for all pulse welding positions because I work for a company that only uses pulse mig welding and sometimes I get that cracking sound in the flat and horizontal and I am tired of cleaning a ton of bb’s.Also I was told you are not supposed to put any motion into your pulse weld bead...thoughts and advice please" (sic) the comment was from our previous video on Vertical Pulse MIG Welding we try to answer as many viewer comments as possible and put out videos that will help our subscribers as well as educate anyone looking for that specific topic.
Overhead Pulse MIG is pretty simple once you get your machine dialed in correctly, for this application we ran a 4F (Overhead Fillet) weld on 3/8" (9.5)mm plate in a T-joint configuration. For our settings we ran a 90/10 mix shielding gas which is 90% Argon and 10% CO2, in order to achieve a true spray transfer you have to have an Argon concentration of 82% or higher. The wire feed speed was set at 165ipm for our E70S-6 .045 electrode and set our trim value at 1.02. In order for the spray transfer to occur, we have to maintain a Contact Tip to Work Distance (CTTWD) of 1/2"-3/4" (12.7mm-19mm). If we run to close, the wire will hit the puddle and make a crackling sound very similar to short-circuit, we don't want that. Adversely, if we run our CTTWD too long, we will not get enough current in the weld pool and the puddle will be very difficult to control.
Trim is a very important factor when we are discussing Pulse MIG Welding. Our Trim value is a fine tune adjustment of Voltage. Within the Pulse Mode of this machine we are using a synergic mode. This means that we only adjust our wire feed speed, voltage is predetermined by the machine. The only other value we can adjust is the Trim. Trim is usually preset at 1.00, from here we have to make our fine tune adjustments. Increasing our trim value will give us a bit longer arc length and a more fluid puddle. Likewise, a decrease in trim will give us a stiffer, dryer puddle. Setting this value depends a lot on whether you are following a Welding Procedure Specification (WPS) or not. For the video, I
found that a Trim value of 1.02 worked well for us in the overhead position whereas a Trim value of .99 worked very well for the Vertical plate video we had done previously. I recommend to get some similar material and set up a mock-up joint to get your machine dialed in correctly. When adjusting trim, you only want to make small adjustments, I typically only make +/- .01 adjustments at a time until I like the way the wire and puddle are reacting.
Now let's discuss technique, as with any 4F joint, I tend to favor the top plate slightly more than the bottom, this is because gravity will be pulling the weld in to place along the bottom plate. Come in at roughly a 45° angle and favor the top slightly more and push the weld pool down the joint. Very little if any oscillation/manipulation is need for Overhead. Be sure to maintain your 3/4" to 1" CTTWD and listen to the puddle and watch how it reacts. You should hear a loud buzzing noise, that is the pulse, any crackling and you will have to adjust one or two things. The first would be ensuring you CTTWD isn't too close, and the second is to make sure you are not traveling too slow. A travel speed that is too slow will cause the puddle to crown up and inadvertently decrease your CTTWD. Your weld should be about 5-6 times the diameter of your electrode. In this case we used .045 (1.0mm) so our puddle width should be about 5/16" (8mm). If you have to run a multipass weld use the same techniques as listed above, and favor the top edge slightly. Always work from the bottom weld and move up. Starting at the top and working down will most likely cause overlap and that is an automatic rejection.
I hope you found the video as well as this blog educational and informative, if you have any questions, comments, or concerns, feel free to drop a comment below and we will do our best to get back with you. Until next time, Make Every Weld Better Than Your Last.
About Jason Becker
Jason Becker is a welder/fabricator with 22 years of field experience in the welding industry and a Marine Corps Veteran. He is also an AWS Certified Welding Inspector and Certified Welding Educator (CWI/CWE). While teaching welding at his local college, Jason pursued his Bachelors Degree in Construction Management from Seminole State College and graduated with honors in 2016. He now works full-time as the co-host for Weld.com.